Thanks, guys. Looking at the reference photos I think I will make it just a bit bigger. Perhaps a couple mm on each edge.
BJ, I ordered a yard of the vinyl, but ended up using about 2/3. That said, the initial blocks I cut for the toes were probably oversized, but I didn't want to cut too small and waste it entirely.
Glueing the toes tonight so I should have boots completed by Monday. Cummerbund, pouches and flak vest should be here tomorrow and I'll do a test fitting. Next up is the belt.