Key fob snap size? Line 20... Line 24?

So, I’m trying my hand at making GB1 key fobs (amongst other things). I’ve ordered all the parts I’ll need save for the snaps, because…well…I can’t figure out what size I need.

I’m using 6 ounce vegetable tanned tooling leather (because that seems to be the thickness of the leather used for my store-bought key fob). That would seem to dictate the need of a Line 20 snap since they’re for 5-7 ounce leather. That would take care of the female side of the belt fob, but it looks like it would cause serious problems with the male side.

The leather on the male side of the fob has to be folded over a Dee Ring and then the male end of the snap has to pass through both layers of leather (12 ounces). I wouldn’t think that that could be done with a line 20 snap… or even a line 24 snap (which is intended for 8-10 ounce leather).

Should I have gone with 5 ounce leather (since I so far can’t find a snap designed to pass through 12 ounces of leather)? And even then, how do you get a snap where the female end fits one thickness, while the male end fits another? Everything I’ve read so far says that you should never mix and match snap parts.