OK, if I got this right, you want six on the belt and one in the tube when you go to the line, but its not set in stone that it will be enuff?? To expand on this a bit, I have read somewhere in the last few days where shotgun misses are not made up in WB?? Why would extra shotgun shells be needed, seems like I see lots of belt mounted spare shot shells for a gun that is pre-loaded and no make-ups allowed?? One or two rifle spares seem pretty common on the belts also, I assume one can replace a jacked out round?? Sounds like there must be some creative stage writers out there who can challenge any normal carry arrangement?
Most pistol rounds I've shot on one stage is 30 = 6 mags. However, if you have a malfunction and pop out the mag to clear, you need an extra mag. Or if you accidently drop a mag to the shelf or ground, you need an extra mag. Or if you move fast a mag may "fly" out of your mag pouch and hit the ground, you need an extra mag. So 6 +1 is what I carry.
You are right that shotgun misses are not made-up, however, I've shot stages with 8 shotgun targets. Also, if you jack out an un-fired shotgun shell you can reload one. My pistol belt has room fo 4 extra shotgun shells and 4 extra rifle rounds.
KingSsnake