Jglar, you can use WW with the Lee mould. The trick is that the core pin must be really hot. On a cold core pin, the slug will stick every time. I found this out by sticking one so tightly that the only way I could get it off was by dunking the whole mould in the pot to melt it off. After that, it worked fine.
The slugs are smaller than even a full choke so that does not worry me. Neither does expansion. A 3/4" hole don't need to be no bigger.