I am replacing a shower stall that I installed about 10 years ago. The base developed hairline cracks in the base after about 5 yrs of use probably because the 3/4" plywood subfloor was not supported adequately enough causing the shower base to flex and crack (the shower floor rests on the plywood). I just bought a replacement round shower enclosure kit and to my surprise, the filler in the base is made of styrofoam! I'm thinking the styrofoam will be compressed with use and allow a lot of flexing of the shower base and it will fail even sooner than 5 yrs. I am considering removing the glued styrofoam and replacing it with something stronger but since the base slopes from the perimeter to the drain hole, it is not too simple a task. The styrofoam is about 1" thick around the drain and 1 3/4" thick at the perimeter. Has anyone dealt with a problem like this and come up with a good solution?