When you say the flange is flush with the floor, I take that to me the flange is slightly recessed into the finished floor. If that is the case there are a couple of ways to deal with the problem. First, use 2 standard size wax rings. the top ring can be the funnel type. A single jumbo thick ring would likely be OK, and a waxless seal would also be OK. Don't try to save $5 or so by removing a funnel from a wax ring.
The flange is not on top of the floor but is flush with the floor since the tile was tiled around it.
I'm unable to find anywhere a jumbo ring without the plastic horn. Fluidmaster and Oatie and another did not have one listed on their website either.
Is their no concern about too much wax oozing into the waste pipe?
So if 2 rings are the ideal in my situation it would be first standard ring would be rounded side down on the flange, 2nd standard ring with horn on top of that with flat side down on the flat side of first ring. That about right?
Another question regarding shims. I understand you dry set the bowl without wax and determine if it needs to be shimmed and place the shims. Are you guys leaving the shims on the floor when you reposition the bowl onto the wax? Don't the shims move out of position?