I tried superglue first with backer material and it didn't work at all. It wasn't just the strength of the bond, the break gap between the teeth also stretches.
Before changing out the belt, you should try cleaning the gunk out from between the gear teeth (holes really) and the belt teeth. This alone can cause timing to go out. Then try tightening the belt which is very easy and covered in my pictures showing how to change the belt

Which super glue did you use? I need to talk with a polymer chemist friend of mine and see what she thinks. Guessing as a chemist that isn't into polymers so much, there is going to be an optimal glue or adhesion method for each specific material and even grades of materials. So will have to see what belts I test with wind up being made out of. Which belt did you order to splice for your machine?
I was also thinking about wrapping the first spliced attempt with some tex45 kevlar thread I have that I'll use whatever elastomeric adhesive I wind up using.

Will do. Did you ever make a Youtube video or have a better write up anywhere detailing? Figured I'd ask again for a link to your best reference.

Regular superglue. In conjunction with the glue, I tried "sewing" the ends together and sewing the belt to the backer with needle and heavy duty thread...didn't work. I just bought a regular replacement belt for that make and model machine. I didn't make a youtube video but I uploaded sequential photos and explanation on how to do it on this forum