Greetings luminance.
I will set my humble point of view here, remember that everyone is different and each of us here will have a little bit other conclusions about what you are describing and asking but I hope we will find a common sense.
From my perspective 25 mg is not enough too. I never go less than 50 mg, except when I want to gaze on dmt hallucinations, without breaking through the hyperspace barrier.
I am quite big and tall, fairly well built according to my age, which is 22. On the one hand my body conditions seems to explain that I am accommodated to high psychedelic trips, with high doses of entheogens.
Nevertheless it is the mind and brain that are mostly influenced by those substances, rest of the body plays the role of delivery and pays its cost. ( I do not mean by those costs that this substances are very harmfull but every drug is a some sort of poison that interrupts normal, usual body functioning.)
On the second hand it is about your mental situation, mind state and how your consciousness have been already developed, expanded. I meditate at least 2 hours a day, morning and evening. My high mushroom trips prepared me well for psychedelic adventures. So on the base of my life I have expiranced and concluded that the consciousness is primary for the entheo-moments, the mystical part of reality. Becouse, it is all about the consciousness that moves through the gates and halls of the mind.
The mind can be compared to a maze with many walls and many levels. At the beginning you are in the center, not even knowing where and you are very vulnerable on the forces that pushes you to go further. Not even knowing where you are going, you listen to the voice that you trust completely and identify with as yourself. It is the mind speaking, wanting you to go on that journey. Sudenly the ego crushes, "you" rips apart and you stand naked in front of gods mistery, the pure consciousness, with no walls, no levels, no separatness, pure ocean, you have left the maze. Now you transcend the maze walls, not moving between them. Your ability to transcend those walls depends on how deep you have expanded your consciousness. Reality is mind, in fact, but it complete picture is more complex than we have in our monkey heads and yes we can transcend our limitations through consciousness expansion.
Your expirance looks fascinating and misterious but remember it is a mind projection. May be your own small mind or the bigger collective mind that we surrender as humans. Both are connected, it is all one, but on the first we have more influence than on the second that we have to obey as human part of it. Our consciousness is above them both.
There is a message in the mind for the consciousness, very methaphoric and poetic also. It depends on your awareness, if you can see it or not. If you interupt the message by your ego, even trying to describe it, by their own meaning loaded words, it disrupts the true face of image that your consciousness stands in front off, not mentioning your personal tendencies. To see the phenomena as it trully is, not disrupted by "you", you have to become or rather realize what you trully are in the very core, which is the pure awareness. The words are direction for imagination but not the true image. That is all I wanted to tell about mental part.
Comming back to the body, with which mind is connected as one organism and also outer/inner mind. Your body influences the mind like a sensor, through chemistry. (It is physicall manifestation of the energies that I have mentioned already overhead. Which are very dense so materialised.) Here all depends how your body metabolise those psychedelic substances into mind expirance. How fast they go to the blood stream and to the brain, including influence on the brain chemistry. How it goes, you feel, nobody can tell it to you, you have to handle with your own being by your self and so with that aspect too.
Your body can be compared to a lab for the mind and consciousness to obtain wanted mind state, range of expirance and abilities. So experiment but always remember about safety and in that case you shall listen to others, read some good literature and bee carefull while crossing the boundries. Couse your body is limited and your consciousness is not. If you try to make the limited body unlimited, you will suffer with the toils and torture of your body to satisfy your desires. Your consciousness will handle even expirance of death, while body will die. Be carefull with doses and chemisty that you apply to yourself.
Now the dose, some people take 20 mg of crystal DMT and some take 100 mg, for vaproization. Those with small doses have less intense expirances but their boundries of intensity have not been so highjacked as those who take much more. They can think it is all there is to know but if they would take more, they would see the limit is far far far far far far.... far and even farther from the range of human sight. (Consciousness and expirance can those two have any limits? No, isn't that so?) On the other hand, as I mentioned before, would and how, they come back after such strong expirance? I heard that 100 mg of DMT at once from vaporizer is enough for a year. (Not tried this dose I still hold 50 mg as mine.) While many people take DMT more often with smaller doses.
DMT is natural body chemistry, it can and have been found in many mammals and every living organism can synthesise this compound from tryptophan. Perhaps the body limits to avoid death from over dose are here much more than you as egoic mind can handle. If you are ready to meet god and unite completely, which is to become one and to be one, good luck. (Send me post card if you return.

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My final conclusion is: it is up to you what you do, all you should care is body, mental capability and enviromental safety. Knowing pharmacology and chemistry of your own body can and is very helpfull in dealing with psychedelic subject. The doses that you have mentioned are safe. The question is what you want to obtain, what realisation, what expirance with the substance and dose you have used? Was it worth, you will see. Remember that this is not a party drug and it have very meaningfull teaching within that moves to the core of all existance, whole life, couse it moves you all and you are life itself. Even bad trips have their meaning and are more valuable than good ones, couse they confront you with what you trully fear, giving you chance to overcome that fear. So do not be afraid to experiment and cross your own limits but stay safe as much as you can. Meditation is very helpfull, it is like care of mental hygiene but much deeper if you lose an "I".
Psychedelics are the keys to many doors, they are more than golden keys to any and every palace of the world, which doors you will open is your responsibility. This is not fun but responsible journey and within it more joy can be found than in any childish fun.
Stay safe and travel well.
Much love and best regards.

Life is Love expressed in infinite ways.
Love is oneness and one is all.
Ego cogito, ego erro, cor sict. - I think, I mistake, soul knows.
If I am that which is nothing that exist but receives existence, what can happen to me, even if there will be no existence - that will be my purity.
http://www.youtube.com/watch?v=Fv2f1EbSy2Y