When our P323 was 8 years old the bottom of the mast was significantly corroded. Evidently the upper bilge slants forward and any water in the upper bilge sits at the mast step. We had to cut off the mast 3" and build a 3" platform for the mast step.
9 years later, we discovered the step was sinking into the platform made of plywood, covered over with fiberglass. The yard manager in Southwest Harbor, Maine said we needed polycarbonate (lexan) to support the compression load of the mast pushing downward. I bought 1/2" thick lexan from the scrap bin of a Plastics place for $1 per lb, $22 for the project. I cut six sheets, epoxied them together; recessed lag bolts into the top sheet then bolted the stack to the keel. Next, I bolted the step through 5 of the layers to hold it in place on top of the lexan. It provides a solid, water resistant support to hold the load of the mast, firmly fastened in place.
Before you start this project, it is vital to mark the location of the step since there is not more than an inch adjustment, fore and aft, in tuning the mast. Mark and be sure to relocate the step in the exact position in the boat.
At least 1/2 of the 323s I've been on have this problem.
Cliff and Bezy McKay on Ceilidh (Kaylee) Hull 261