I've been working with cyb's tek now and this was my 3rd try.
I have not been able to break 0.5% yield. From what I have read my yield should
be better than that.

I use 250 grams of powdered MHRB in a gallon ziplock.
I add a liter of water. Freeze overnight thaw all day times 3.
Place in 5 liter erlenmeyer flask, add 100 ml of white vinegar diluted with 100 ml of water.
Ph is less than 4.
Place on heating pad for 8 hours, flask is never so hot I can't pick it up with bare hands.
Add 3 liters of saline (80 grams salt per liter).
Basify using 100g of NaOH dissolved in 250 ml of water, ph is now 12.45
On heating pad 2 hours.
Add enough saline to bring fluid level up so that exactly 250ml of solvent will fill the flask.
6 pulls done of ~225ml each using heated naphtha. Pulls are done as follows:
Heat naphtha using lab hotplate. Add 250 ml of naphtha.
Cork flask. Flask is tipped back and forth gently for about 15 seconds.
Allow layers to separate. repeat tipping and separation X3.
Draw off solvent containing product, replace with heated naphtha.

All solvent containing product placed in pyrex dish, reduced by fan till milky.
freeze precip. results in beautiful white powdery crystals, no gunk.
but crappy yield.

Am I leaving product behind in the mother liquor?
Should I be doing more pulls?
Should I be using a larger volume of solvent (tried smaller volume, yield was worse!)

thanks much for feedback

You're technique seems fine , although IMO I think 3 litre mass bottle would be better for a 250g extract !!

And also 250ml naps is way to much especially trying to freeze precipe with such a large amount of naphtha try using 75-100ml per pull and try shaking a bit harder , you'll be surprised at how hard you can shake without an emulsion , and pre evape atleast half ! You can't just go on it going milky because it will turn milky in front of a fan no matter the amount of naphtha ! So go on volume not cloudiness ! Also are you sure you've got quality bark ????

From what I read you are doing everything exceptionally. What is "crappy yield" to you? Low quality bark can have as little as .5%.

You have over 4 litres of solution...that's crazy.
You could do 250g in less than 2 litres.

225ml is too much to pull with...try 75ml

You DON'T just double up all the ingredients exponentially...that's not how it works.
Understand the process before doing larger amounts.

Also it's All down to the quality of your bark. You can only extract what is available.