Rate of advance on 1.5 inch piece
You are trying something difficut.
I suggest (in degrees F)
11/hr to 510 no soak, 17/hr to 1000. Start checking from about 600, as there will be a lot of heat work put into the piece by this time. It might even be tack fused at a lower temperature.
Anneal cool should be on a slower schedule than previously, as the tacked parts will try to pull away from the big block.
So I suggest 3.5 days for heat up and 2 days for cool down to be sure everything is secure.
Is there another way you can do this?