Primavanserin does seem like an obvious no brainer concerning HPPD/VSS. Probably a lower dosage over, I don't know, six months or something. Sort of surprising nobody has gone there.
Here's a link to part of that guys book(post lsd syndrome) if your interested
https://books.google.com/books?id=KKYh00o69TUC&pg=PA58&lpg=PA58&dq=thiothixene+lsd&source=bl&ots=TzolEssc07&sig=q6EOTJuaH09Ok7CWdScOWTQn3co&hl=en&sa=X&ved=0ahUKEwiA3_PN8rTUAhWG6iYKHbeIDKYQ6AEIRTAD#v=onepage&q=thiothixene lsd&f=false