I just had mine repaired during the annual. Patched a small hole in the bottom, some kind of fancy paint and its back to doing what it does best - keeping the battery out of sight.
My battery box has four holes on the bottom -- the dimples that the battery sits on. They have worn through, probably because of acid from the old Gil battery, battery movement, and time. At my last annual, the mechanic noted the condition (it has been noted before) but allowed me to continue using it. Hopefully it will continue to maintain acceptable structural integrity and I won't have to replace it. How much do these things cost? Are they hard to replace?