Ahhh.

never had Ubrakes. Went from side pull to vbrakes so until your reply, I didn’t realize the mounts were opposite of v-brakes.

I think your best bet is probably to overhaul what you got. Install the stickiest brake pads you can. And go with it.

I don’t know if the bridge at the seat stay will take dual pivots? Or if dual pivots will clear your tires?
Or use a canti conversion plate at the seat stay bridge? Just some ideas.

I ran odyssey 1999’s when I was a kid. Pretty good for side pulls, but I think you’ll need a longer brake lever to make up the difference in braking power over Ubrakes or Vbrakes.