To clarify: I very gently stir every pull for 30 seconds then let the solvent sit for 2.5-3 minutes, then decant.  But even that gentle stir is probably unnecessary since the cactus is so well broken up if all the pulling is done within 30 minutes.  After 30-40 minutes the cactus begins to stick together and thus we conjecture it would be slower for the mescaline to migrate out to the solvent.

Just like hot water pulling goodies out of tea leaves within a few minutes, we don't have to stir the water vigorously.  Same with the mescaline freebase and ethyl acetate.  The ethyl acetate seems to be very effective at pulling the mescaline without physical agitation.

I've added 5 mg/gram, 15 mg/gram, and 20 mg/gram with different attempts and they all resulted in precipitation within a few minutes of vigorous magenetic stirring.  I added the 5, 15, or 20 all at once (nothing incremental).  Yields were all basically the same.  The only difference is more of the 5 mg/gram xtals stuck to the walls, requiring a warm water wash to get the last of the xtals out of the jar.  The 15+ mg/gram xtals pretty much all come out of the jar by knocking them off the sides with the spinning stirring bar then rinsing with ethyl acetate, thus no warm water wash/evaporation step is needed.

I believe the 5 mg/gram xtals are a little fluffier, thus more sticky.  The 15/mg and 20mg/gram xtals are smaller and more dense, thus they don't stick to the jar walls as well.

I did a comparison in Run #3 - Jar (B) versus (D) of 5 mg/gram versus 20 mg/gram and the 20 mg/gram had visibly less precipitate.  But after filtering, washing, and evaporating, I found the yields were basically the same.  The 5 mg/gram just looks like more when floating around in the jar because it is less dense.

Gentle, fast pulls and bombing with plenty of citric acid appear to be the primary differences between my successes and head-scratchers.  Bombing immediately rather than letting the extract sit around may be a secondary difference.