There are a lot of dough recipe's on the forum and many have shared recipes producing success w/ KABF. It would be helpful if you posted a top-side pie/slice picture as well as a bottom-side slice picture.
I don't have my notes handy but I'm pretty sure I've scorched 00 flour on a cordierite stone at 750F in a few minutes. Keep in mind that the cordierite conducts better than most firebrick. If you are going to throw a pie on at 725F (measured by an accurate IR thermometer), just pick it off inside the first minute and move it a bit. If you are still having a problem, put a screen under the pie to finish it off, then next time, throw the pie at a lower temperature.
That's one big, thick slab of cordierite. You must really be throwing the BTUs on it to get to 725F in 30 minutes. I'm assuming that you heat the stone then rotate the burner to blow up over the top of the pie and use the residual heat to cook the bottom. (True?)
I only use a 1/2" thick stone (x ~15" dia) and when heated to 700F ish, I can turn the underside burner off when the pie is thrown and cook equally well just with topside heat - so your 1" should be more than enough to cook a pie (or maybe 2).
One shouldn't assume that the rectangular stone, heated by a round underside burner, results in a uniform temperature across the surface. You might want to map several points on the stone and check the gradient. If you get something interesting, pls post.
I'm looking forward to seeing how this works out.