Each substance has a different effect on DMT visuals so there is no 'law' that says visuals increase or decrease with MAOI dosage.
A substance may also alter DMT visuals, rather than increasing or decreasing them.

With Caapi, most of the time, a higher dosage in the first place prolongs your experience. Another effect is that the higher the dosage becomes, the more difficult your coördination will become and the heavier your body will feel. I personally find that visuals are not so much increased or decreased by caapi, but energized.
But each type of caapi (yellow, white or red) is different as well.

Rue also alters the visuals of DMT, but in a different way than caapi does.
Caapi is by far superiour to rue.

Other types of MAOI used, will probably leave their own unique mark on the effects of DMT as well.

I brewed three teas: 1) concentrated Rue where 22 ml was the equivalent of a 3 gram dose extracted three times using acetic acid. 2) Not so concentrated Caapi where 75 ml had the equivalent of 28 gram dose extracted three times using acetic acid. 3) Mimosa H. Tea where 35 ml had the equivalent of 7 grams Mimosa H using lemon juice to extract three times.

My girlfriend took 3 small vials of these extracts to our doctor who knows what we're up to. He is an excellent holistic doctor who has cured her of secondary progressive multiple sclerosis (not curable by the commonly practiced high dollar $20K/year beta interferon pharmaceutical route), so we both trust him and his methods implicitly having 5 years experience with him now.

He judges the efficacy of medications and vitamin supplements using Meridian Stress Assessment, and he requested that we bring some of our 'tea' into his office when my GF was to be tested to assess the need for additional IV treatments to treat her MS. Neither my GF nor the technician knew the contents of the vials, so it was a 'blind test'. The result for my GF was as follows:

1) Rue tea was not beneficial, but it was not detrimental
2) Caapi tea was VERY beneficial
3) Mimosa tea was not beneficial, but it was not detrimental

I plan to bring these extracts in to my MD's office to have the same testing done on myself, and plan to bring some extracted spice FB and fumarate forms in for MSA testing and see how I test against them.

We have had two Ayahuasca experiences experiences using extract #1 and extract #3). My GF had a mild, pleasant trip with a fair amount of purging during our first experience and I had what I would consider a threshold trip. On our second trip, I had a much more intense journey that lasted almost 4 hours. My girlfriend just experience nausea puking her guts out but not embarking on any sort of journey. She is not open to a repeat of this, but is open to the possibility of smoking DMT and trying pharmahuasca.

I have read a lot of reports about using Rue versus Caapi and my conclusion is that many people do not handle Rue very well, and that on the other hand many report that Caapi is gentle by comparison. It is my thinking based on only my GF's MSA result that Caapi would for her allow a better Ayahuasca experience. This is minimal evidence, but based on other testing she's done using MSA, I trust the result. I am very curious to get tested using MSA for these ingredients and compare the MSA result again my experiences including a future planned journey with Caapi / Mimosa.

Any feedback from anyone? Has anybody had MSA testing done of any sort especially against entheogens?