My 1986 catalina rigging is new, but have noticed over the past few years that the leaward stays have excess slack regardless of the rig tune. I also noticed that the mast support arch has a few gelcoat cracks located near mast step visible from inside the cabin. On the cabin roof, the area imediately surrounding the mast step is sunken or depressed by about 1/4 of an inch. I suspect that I have either some water damage in the wooden arch and/or rot in the wooden compression tube/mast step in the bilge area. Has anybody experienced a depression around the mast step but found the sole problem to be not the arch, but just the compression tube? (The arch cracks have been present the entire life of the boat.) Assuming I have to replace rot at the bottom of the compression tube, does anybody have a replacement material that they feel represents good durability and realtive ease to work with? In reading about some of the previous solutions- steel planking will rust, and concrete seems like it might reintroduce moisture where it contacts the still solid portion of the compression tube. Thanks.