My speakers cans were installed under the tower at the MFG. When I lay the tower down in the garage, the faces of the speakers rest on the upholstry with a lot of weight. I simply cut a piece of 4X4 about 2 feet in length. Open up one of my V-drive compartments and prop the piece of wood up so the tower will rest on the wood.
I've seen other posts where people make PVC pipe stands that the tower will rest on as well.
Hang them under, it looks better.