im really nervous- already had dreams of this tipping-
cannot find a square cake stand to save my soul, going to try foam board and dowels. not sure other than just resting the board on the dowels to stack this puppy!!

That's what we usually use. I never use dowels though, I use bubble tea straws. Unless you SPS, which is the safest thing out there. In the How To part of the forum, there is a sticky towards the top called SPS instructions.

Definitely use SPS!!