Anyone use Thermo-12 Gold flat block insulation?

[ceeyahd1]

Building a 42" barrell vault and I am in search of insulation boards, INSBOARD min. quantity is 36 sq ft which comes out to over $500, Thermo gold 27 sq ft. is around $100 but only to 1200 degrees. Has anyone used this brand of boards and how do they compare to INSBOARD? I am in So. CAL if anyone knows of a better source or brand.

Thanks for your help.