>>538613754
That's my sentiment. You need to be explicit regarding that anatomy. Some models grasp it better than others, but if there was any doubt, I'd make sure that kind of detail was included.
>>538613840
Right, I was just contextualizing the front pussy for the uninitiated among us. Not everyone is in on the monstergirl fucking circuit.

You're free to imagine any number of vaginas (or whatever kinda hole you need) on any character if you like. My preferences aside, I don't mean to police the creativity of others. I just don't like the front pussy being a convenient way to bypass the HORSE PUSSY. To your point, the front pussy does not accommodate standard humanoid sexual positions in its entirety as well. Given the tallness most horses' legs afford, the average human male could not enter them frontally while the centaur was standing. At least not without some stepstool or (as you'd prescribed) doing pull-ups on their shoulders. In that way, the centaur needs to be a stunted munchkin if they hope to enjoy standing sex with a human with a front pussy. FP offers more options while lying down for sure.
>>538614464
If it's not documented anywhere, write the lore yourself. You could make it an oral-focused exchange if you want to strictly adhere to the animal you're referencing. (I'm assuming this snail has reproductive organs around its head?) If the exchange is interesting, most monstergirl fuckers will do whatever it takes to get the job done.