I've done this with a mix of psilocin/acetylpsilocin. I had 4-aco-dmt hcl that was not stored dryly enough and absorbed h20 (the hcl appears to be hydroscobic) to form a brown goo. I took it (~700mg) and added 700mg of lime and a ml or two of water to make a paste.
Then i let it react & base stirring liberally over ~1hr. Bluing started to appear at ~30min, and i speculate that that is an indication some of the 4-aco had converted to 4-ho. Whether it happened before i based it, or during the 30 min or so it had been in base hydrolysis conditions idk. At 1hr i added mgso4/naso4 to dry it out almost all the way. Dumped the crumbles out on a glass dish and powdered it until fully dry.
Pulled 4x with dry acetone after adding the powder back in the glass weighing jar, and then proceeded to fasa the acetone immediately. I figured the longer i worked with it as the freebase, the more degradation to inactive byproducts. After a good amount of fasa & stirring until it stopped clouding, i decanted off the tone and was left with off white semi silvery crystals. Scraped them up, powdered and it got a bit lighter.
Seemed to work very well compared to a dmt fasa, and the yield was 500mg of the fumarate. Some was left in the solvent, and precipitated later, or when the volume was reduced, but i was happy with 500mg of this from 700mg of degraded/ing hcl. Bioassy of the stuff felt distinctly different than 4-aco, and it feels too consistently different to be placebo, i speculate that a good amount is now psilocin fumarate. It seems on par with the potency difference with hcl/fumarate, and 20mg is about as active as 15mg of the 4-aco hcl. Seems fairly pure and active from what i can tell.
It would be interesting to see the results of doing a lime fasa drytek on a methanolic/ethanolic extract from mushrooms. I bet if you were careful enough you could get at least a decent yield of the fumarates that may be more stable for storage, or different pharmacologically/chemically than natural mushroom alkaloids. Plus, crystalline mushroom alkaloid fumarate crystals :want: :want: :want:. I'd try it if i had access to enough mushrooms to make it worthwhile, but i would feel confident it would be worth the effort though.