I like split rivets soldered to the back or #14 belt rivets and a liner on the inside of the belt to cover the inside of the belt. It might help to see what the conchos are shaped like too.If nothing else small Chicago screws will do the trick too,....
I have the same die, I made split rivets and put 4 on each. If you use a small piece of urethane 95 duro, and press those, they should come out with more definition.
Run the 12 gauge wire through your rolling mill to about 1/4 of the thickness.
Cut it into 1" lengths, fold it in half with your arbor press or pliers and solder it down at the fold... be careful not to let the solder run up the "legs". You just want to attach it at the fold.
Punch holes in the leather to accept the split rivet - push it though and then clip it to the length you need, if it's too long
I use a small cold chisel to start the spreading, then a small mallet or hammer to flatten.
You'll do just fine... come back and explain how the solder ran up the split the first coupla tries.
People learn from hearing that that kinda thing happens - unless you do, what?
B.
Several ways to solve that problem. One way is to make sure you spread them slightly before you tin them. Another way is slide thin titanium sheet between 'em before you tin them. Another way is to use yellow ochre or red rouge paste before you tin them. Another way is to simply learn heat control... and on and on and on...