I'm installing a new toilet soil pipe in my bathroom and when I attach the 4" PVC elbow that will attach to the flange, the pipe comes more than 2" above the subfloor. Any ideas how I will be able to get this flush against the tile once it is installed? Also, I purchased a 3"/4" flange to installed, does this have to be glued in or does it just rest on the tile and in the soil pipe? Thank you.