Wow, this is an old post brought back to life!

Solution depends on what the problem(s) is/are. Leaks in the tubes only or leaks and structural?

Fill all 4 tubes with water and determine which are really leaking. If only leaks then the epoxy or maybe even silicone may do the trick.

My repair involved structural as the front tubes had separated from the base sockets so I did cut in ports and glassed the base. Worked like a dream and not that bad a job.

At one time Hobie made vinyl plugs for the tubes to keep water out.
Good luck, TG