Lower the doses of your tryptamines if you try combining since there are relatively few reports on this plus synergistic effects are hard to predict.
It's very possible you need less than half of a normal dose of tryptamines if you put two together though it's also possible the separate doses are higher than half. To be sure, when you experiment, assume that you need only low doses and next time steadily increase the dose. There is no rush to try and get it right the first time unless you are okay risking more than double the intensity you are expecting and other types of effects you weren't even thinking of.