I wonder how that might be chemically different than fused silica which is used for telescopes. I understand that is about half the COE of pyrex whreas your numbers are right there in the borosilicate range.

This is interesting and I wouldn't mind getting my hands on a couple of 20" ends. I would recommend extra procautions as the grinding dust should be lighter and more dangerous than regular telescope glass materials. You might want to ask you friend about Osha guidelines and HMDS info.

Good Luck,
-Rick