Wow, it's new to me that the old ball mold is still in production. As a wannabe GBC builder, that's great news. I actually just ordered 15 soccer ball, so few becouse they're quite expensive on bricklink...
IIRC standard GBC balls are 14 mm in diameter. Zamor spheres are much bigger, and a carefully tuned GBC will not accept them. The biggest problem is passing (or not) inside a 2 wide gap, and that makes all the difference :)
I've read in different forums that some builder advocated using zamor spheres in GBC as they're easier to find.
