Try using sodium carbonate.
SWIM has been unsuccessful extracting 5-MeO-DMT from any plant when using a stronger base. So I think it’s destroyed by high pH values, or more specifically destroyed by hydroxides. I don’t understand why hydroxides would do it. I know hydroxides are bad for bufotenine, which is 5-HO-DMT, and very closely related chemically to 5-MeO-DMT. Hydroxides are also bad for extracting psilocin (4-HO-DMT). Possibly the HO and the MeO on the DMT molecule are not stable enough to withstand the hydroxides. With DMT, high ph doesn’t matter, but with 5-MeO-DMT, SWIM’s tests seem to say it does.
SWIM has not tried this with pure 5-MeO-DMT. So he doesn’t know if the 5-MeO-DMT is being destroyed or somehow the plant sources used in extraction just don’t extract well using hydroxides. Maybe a lot of soap is forming, and that’s the issue.