Forgive me if I'm off track here, but I wonder at the advantage of the modified Lee mold over one made to the dimensions you're looking for. For example, I've been using this mold from Accurate Molds:
http://www.accuratemolds.com/bullet_detail.php?bullet=51-320S-D.png. Since it is a custom mold, Tom can make it to whatever (reasonable) dimensions you ask for. You could deepen or add lube grooves, change the crimp groove, change the meplat, etc. without additional cost. The cost, by the way, is quite reasonable. I don't know how much it costs for the Lee mold, then to have it modified, but for not
too much more, you could get exactly what you want. In fact, you can specify the diameter and, depending on your alloy, it will be very close if not exactly right. I use my bullets as cast because I had him make the mold to match my bore.
Again, I might be missing some advantage of the Lee mold. I'm very new to Spencer shooting, so I almost didn't want to reply for fear of saying something foolish, but we're all friends here, right?
CC Griff