Are you looking to smoke this or take it orally?
The problem I see with oral consumption is that it would take a ton of caapi leaves to achieve MAOI inhibition, an unspecified ton, because the alkaloid content in the leaves seems to be so variable. You should use vine. It's also worth noting that some people find ayahuasca+mushroom journeys quite difficult. (not to say you shouldn't exsperiment)
If you weren't aiming for full MAOI inhibition, then the addition of DMT to the mixture would be a waste; more or less you'd be having a psilocybin trip with a caapi edge to it.
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