I have a 90ish year old house. I tore out some rotten hardwood floor planks in the area under the toilet. Subfloor is fine. The new hardwood floor planks are about an eight of an inch shorter than the original ones. Wondering if I can put something under the new hardwood floor that would not only raise the planks to the same height but also improve the waterproofing so the subfloor wouldn't get wet even if the toilet leaked. A fitted painted piece of plywood? Would it somehow impact the rest of the floor to have something under that area of floor?