correct way to level cast iron tub
I'm in the process of installing a cast iron tub with a friend. He and the plumber set it on wood shims to level it before hooking up the drain. It is on a new 3/4" plywood floor that has been reinforced to take the weight. No problem there.
My concern is that wood shims in 4 places along the edge won't support the weight long-term and will crush down, creating a crack between the tub and soon-to-be-installed tile.
What is the correct way to install the tub, or is this acceptable?