Designing the 2-diameter paper patch bullet.

[beltfed]

I meant the diameter of the band somewhat less to accommodate the patch.

Yes, you have the diameter of the base band such that it patches to a nice snug, but slip fit in the fire formed neck and any freebore in the chamber. At the same time, you need to set the body diameter such that it patches to snug, but slip fit on the lands.
So, you need to match everything up to the thickness of paper used.
beltfed/arnie