Very interesting....and very nice work. Well done to you and Dad! Very nice results.

I have been using a Miles Gilbert jig I got on sale at MidwayUSA and a 4" wide benchtop belt sander. I hook it up to a shop vac, but there is still rubber debris all over.
I get a very smooth edge on the pad if I am careful. If you were closer, I'd bring it over and you could use it. I'm not saying it is better or not...and I don't have the pictures to show yet.
I have done two and I can get them to fit the stock rather well. The advantage of the jig is that I don't have to worry about damaging a prefinished stock. The disadvantage is that it is much harder to get that "perfect" edge that you can get by doing the pad on the stock prior to finishing.

I use a lot of WD 40 to lubricate the pad and the belt, and I freeze the pad prior to sanding. Those two measures seem to help with the smoothness (smoothicity?) of the finished product.