Back when i had gotten some 5-MEO, i tried a test dose of like 5mgs in my homemade pipe, it hit me pretty hard so i sat the pipe down and realized i wasn't yet ready to enter 5-MEO space. So after the effects were dying down i smoked on some Rue seed to see if i could extend what i was still getting from the 5-MEO, didn't notice any potentiation or anything and soon the 5-MEO was completely out of my system. So about an hour later, i wondered if there was any 5-MEO left in the pipe or if i had gotten it all the first time, so i hit the pipe and took a big inhale, and i do believe whatever i got from that second time was no doubt potentiated by the smoked Rue. I started freaking out because i didn't want to over do it lol, but all was well.
I do want to try 5-MEO Changa at some point, however, it's important to note that Harmalas inhibit CYP2D6, which CYP2D6 metabolizes 5-MEO, so there's going to be potentiation of 5-MEO dosage from the CYP2D6 inhibition, but also because of the MAO-A inhibition there's going to be additional potentiation, so i highly recommend dosing low low on the 5-MEO if attempting this, like maybe start in the microgram range and you probably wouldn't need to go over 5mgs, heck even 1mg possibly. Also keep in mind that 5-MEO inhibits the reuptake of monoamines like Serotonin, Noradrenaline and Dopamine iirc, so that with the MAO-A inhibition is definitely some cause for concern, however i believe it's doable if one is really careful and safe.
With all that said, 5-MEO is not as physiologically safe as DMT is, and 5-MEO has caused a few deaths in the literature iirc, especially combined with Harmalas, so it's not a safe combination like Harmalas+DMT is, but i don't think it's too risky to safely attempt, just know that there is a potential risk for OD with 5-MEO (especially with Harmalas in the mix), so you proceed at your own risk, but imo don't let that necessarily scare you off, just be safe and extra cautious if pursuing this route, and probably best to not go for oral 5-MEO with oral Harmalas, imo, although i'd be curious if anyone has.