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you mean HPPD?
About combining psychedelics I have varying opinions, for instance I see little use in combining classic psychedelics like LSD or mushrooms since they serve in almost exact the same place or way. Combining two 2C-X compounds on the other hand appeals to me because some of them really have much more particular characters and two could synergize into a distinct different animal.
The more drugs you combine the more unpredictable it gets, which is a problem if you want to go from zero to 20. The low doses make it less of a wild shot, but it is still a very complex question what kind of doses would combine to what level, a level that should not be underwhelming or overwhelming. Change the dose of one of the 20 drugs and you might very well have a different ballgame.
Some natural products of course have mixes of alkaloids: weed, mushrooms, cacti and some DMT-containing plants can contain complex mixtures although most often the most are secondary alkaloids (or terpene-like active compounds) that only modulate the primary alkaloid(s), which may be only one or two or so.
Having said all this it is an interestic hypothetical question at least what happens if you mix 10 different 2C-X compounds all in parts proportionate to their potencies. It should be obvious that titration should start very low with this because it could have a very unexpected effect in terms of for instance dose-response curving.
I mostly feel like predicting that it would seem like a very generic 2C-X feeling as is sometimes reported, by that I mean the part most 2C's have in common. That part of the action could be synergistically additive while the other more unique sides of the compounds drop off because the partial dose is too low.
But who knows, I might be completely wrong and it could feel very special and much more natural. Part of the distiction between natural and synthetic drugs and the effect they give seems to be that synthetics tend to feel quite pure, which can seem a little alien, unnatural and unearthly, although to many others it is a pretty positive aspect. Maybe the feeling of a mixture of synthetics would take away that synthetic feeling and make it feel more rounded and balanced.