OK...it takes a long time for me to conduct the test due to my laziness, so here it is...
The 8mm fisheye were tested with a full frame, 1.3X, full frame + 1.4X telecon, and a 1.6X crop sensors. So here are the results:
Taken with a FF:
FF + 1.4X telecon:
the 1.3X is usable yet, it still needs a minor cropping, and the FL is at 10.4mm. While at the 1.6X it is at 13mm.