Everything looks great, except for the toilet flange, which was installed a bit too high. Well, it's not fair to say that, because it's installed as far down against the floor as you could possibly install it, but still sticks up far enough that it's not possible to seat the toilet and have the toilet resting on the tile floor.
I tried putting shims under the edges of the toilet first, and it seems to do the trick, while leaving a little over 1/4" gap between the floor and the base of the toilet. Not acceptable. In addition, I am still able to jiggle the toilet base enough that I'm sure someone could knock it off the shims if they bumped into it. Not a risk I'm willing to take.
So, any suggestions on how to correct this excessive gap? I'm trying to avoid having to rip up the floor, break out the concrete, and splice in a new section of waste pipe so I can start over. Is this the only real option? any suggestions would be most appreciated.