If you're particularly concerned about lye contamination you could always crash with ammonia instead.
Brennendes Wasser has done the most extensive comparison of vaporisation properties of various substances,
harmalas included, and their salt forms so I'd suggest checking that particular
thread.
Caapi contains a broader range of unique secondary alkaloids that may or may not contribute to the spectrum of caapi's effects but I would expect the glycoside like ones (i.e. those with sugar-like molecules attached) to be less suitable for vaporisation, for example. It's perhaps a question of whether you noticed any specific 'caapi-like' quality from the crude extract that you'd like to preserve. One way of homing in on this would be to compare the effects of the precipitated freebase material.
Another way of taking this further might be to examine the qualitative and quantitative anylyses of caapi and determine whether any of those secondary components appear to be of pharmacological interest to you. That may turn out to be an endeavour equivalent to writing a doctoral thesis, however! :lol: