If swim goes with the enhanced leaf method.
Is 91% isopropyl alcohol okay?
Or does it have to be 100%?

i would use everclear or methanol. isopropyl has been know to mess up harmalas and make a new compound called harmala red. iso works for some people, and not for others. try dissolving a small amount of harmalas in it first and evaporate to see if its red.

also use 99% it will evaporate much faster

today I was crystalising some spice with 100% iso to see how it would go.. there seemed to be a small amount of water in it :/

High proof grain alcohol is preferred, but isopropyl will work, even 91%, although you'll just have to evaporate more water due to the 9%.

If you plan to disolve harmalas in the iso, heating the iso in a hot water bath helps to dissolve the harmalas (as harmalas are 'slightly' soluble in iso). Never had an issue this way.