I've vaped 25i on a couple of occasions & it is effective. However smoking it (i.e. actually burning something) seems like a bad idea as it would likely deliver an unknown amount, thus skewing your dosage & making any future doses based on previous experience dangerous. Pyrolysis is imprecise.
My method for vaping was making an etoh solution & putting 250 micrograms worth in several test tubes, letting the etoh evap, then applying heat via a butane torch & inhaling the vapor with a glass tube, titrating up 1/4mg at a time. Never went above half a mg. Unless you're completely confident in your measurements this should not be attempted.