Velo Mule

I use West System epoxy and carbon fiber to repair lots of stuff that I have, I have not done a seat, however, it would be simple enough I believe. West System sells carbon fiber unidirectional ribbon that is on a roll rather than a woven mat. This is what I would get for this repair. I would mix up the epoxy, thicken it a bit with colodial silica and brush it over the damage rail and seat. Then apply lengths of the carbon fiber over the repaired area first going in one direction, then the other. You may want to have more layers going across the rail and fewer in the direction of the rail.

If you want to make the rails float, you could try coating them were they will be covered by the epoxy with Vaseline or something similar to prevent the epoxy sticking to it.

Alternatively, if you like the seat enough you could make a mold of the seat and start off making a new seat. You will still have to attach the seat rails to the seat though.

I find that epoxy is easy to work with and I like using carbon fiber for the repair because the I can control where the strength is based on the direction that I apply the fibers.

I haven't ordered from West Systems in a long time. I don't see their carbon fiber ribbon on their website.