It works for walking on but vehicles go right through it. That's what I'm worried about. I wanna use this brick for a mountain to ski on
Welp, the collision you want is actually concave.
If you can find a line that skips over a vertex while still remaining on the outside of the model, it's concave...

I have no idea how the engine decides if something works well or not. Don't the concave corner ModTer pieces have proper collision?