Mostly the wing and the angle. You'd also be pushing the trailing edge of the prop. When you're in front of the engine, you can rest your fingers flat against the blade of the prop. Pushing against the trailing edge would, for me, make me want to curl my fingers around to the rest against the blade.

It really isn't at all awkward to hold the model from the front. You've just got to be mindful of the prop, which is something we all need to be anyway. Like anything in the hobby, if you're uncomfortable doing something you probably shouldn't do it--the point is to enjoy yourself.