Paul,
Nearly every Beaver of that vintage has the issue and there are not a lot of good choices. The "top shelf"
way of handling this is to sand all the peeling surface until all the loose clear is removes and the edges are feathered, solvent wash it, mask and recolor coat the original color and then spray 3 coats of the best automotive clearcoat that you can buy. I would use a PPG product but there are others.
So this would be an experiment, take one small area up top where it is not so visible and see if you can remove the loose clear by gently scraping with a razor blade. If you can get to a good edge with good adhesion while leaving the base color coat. If the visible loose clear is gone then solvent wipe, scuff gently with a red automotive scotch bright type pad, solvent wipe, and you could try and automotive clearcoat spray, something like this.
https://www.amazon.com/Spray-High-Gloss-Clearcoat-Aerosol/dp/B0043B7UQYIf you can get a technique that works then you could spot repair some. I think in the long run you would be better off just having the whole job done properly given the clear on the roof is reaching its end of life as a material and you would be chasing this issue forever as a spot repair. Really there are no good inexpensive answers...
Later Ed