I know this will not help you at all now BUT I once got my vessel form stuck in a metal mold and wound up putting it back in the kiln upside down and brought up VERY slowly (25 deg. per hour) up to (I was going to go to 450 deg. F. BUT it dropped out at 400 deg. F. ) I had layed out 2 layers of 1 1/2 inch fiber underneath for it to fall onto and it all was SUPER. I let it cool down slowly toooo! , but not sure of the correct cooling but I went 50 deg. Per hour down to 80 Deg. F.
I NEVER peek below 1000 Deg. F. and never open until it has reached room temp. (totally eliminating the thought that I thermal shocked it.) I have also had EXCELLENT results slowing the rise in temp to 50 deg. per hour. but once again my pieces are usually 3/4 of an inch thick.
When tack fusing , I even slow down to 50 deg. per hour when slumping as it is thick meet thin meets thick again and well, I would rather it turn out than go tooooo fast.
You are QUITE close to the elements tooo , so again I would slow it down. BUT you did mention that it did not break on the way up because you did monitor it and look at top temp. Is this correct.
So not sure if I addressed many questions , but just how I am having success of late.
Lesliehttp://www.twinvision.fusedglassartists ... s2009.html