I had my toilet flange roughed in at about 5/8" above the subfloor (was going to do 1/2" underlayment and vinyl. But, i changed my mind and now did 5/8 plywood underlayment and ceramic tile. I asked my contractor laying the underlayment to remove the 5/8 standoffs I had under the 3 flange screws and get the underlayment under the flange... well, I guess it was my fault for not say ALL THE WAY under the flange... since it got it about 1/4" under the flange all the way around. It is secure and my plan is to screw it into the subfloor with long screws and then fill the open space under the flang left by not pushing the underlayment all the way to the drain pipe, with thinset. Does anyone see any problem with that, as long as it is solid and secure?

I plan on adding an extender to bring the flange slightly proud of the finished floor. What is the best way to install this? Just silicone caulk to the floor flange?

I assume that the toilet does not exert any downward force on the flange, correct? And the reason for making sure it is secured is because it is the transfer piece through which the toilet bolts are secured... correct?

I just want to make sure I am not missing something here before I do this.

Also, what is the BEST wax ring to use? The kind with teh plastic flange?