Longs,
I was afraid of that. They build the molds such that only a small range of hook sizes will fit them. I've modified the molds to take different hook sizes in the past, but it's not something a supplier would do unless you need a lot of jigheads.
The split shot thing works really well. If you add a drop of Gorilla Glue before you crimp it (you have to let it cure before you paint it/tie the fly), it won't come off.
Good luck!
Buddy