I'll be embarking on a similar project on my desk-stepped 32 this winter/spring. For me the issue is not an (evident) depression at the foot of the mast, but a sagging inside the cabin between the two companionway supports that hold up the mast.
I believe the original structure is a substantial piece of solid wood placed athwart the companionway, atop the companionway bulkheads, and glassed above and below. It's likely waterlogged and rotting, not unlike several areas of the balsa core that I have previously repaired and documented here.
My plan is to:
* Remove the aluminum mast step, which has been in place for longer than the 24 years I've owned the boat
* Cut out a rectangular area of the skin below the mast step with a shallow cut with a diamond blade on an angle grinder, increasing the size until I've plumbed the extent of the damage (sorry, no Dremel for me on this kind of project!)
* Dig out the rotted/waterlogged/whatever wood
* Replace the wood with a slab of G10 of whatever thickness is necessary - it may be 3/4" or more, which is expensive, but it will still be a lot cheaper than hiring a yard to do this somewhat straightforward work
* Replace the skin with a 3/16" piece of G10, tapered on the edges and glassed to the edges of the hole
* Paint to suit
I'm a bit concerned that the slight curve of the deck underneath the mast will require some fancy preparation of the G10 slab, but I guess I'll find out once I start cutting.
