How do you fix big R-15 character models falling partly through ground?

I've been testing with some R-15 character models and I want to make it so that the player spawns as a big R-15 character model. What I quickly realized is that the model will fall through any surface until its hips. I looked more into it and I saw that this is because the legs and arms don't have cancollide on, but the rootpart, head, and the torso do. I tried turning on cancollide on the legs and arms to see if that would work but it doesn't work. I've also tried scripting it (which I doubted would work), but no luck.

Is there a way to make it so the npc correctly stands on the ground without sinking through the ground until its hips?