You will find that combination will work very well. We built our forge the same way. A 20 pound propane tank, 2 1 inch layers of ridgized kaowool, a half inch of Satanite and then bubble alumina all around over the Satanite. The only difference is the burner, ours is a single burner Gaco kiln burner and it reaches welding temp in no time.
20 pound propane tank forge in progress - Gas Forges - I Forge Iron