No fatigue associated with that area of the cabin top. I've never noticed any flexing or movement related to that area either. It's easy enough to access/inspect as there's a separate panel independent of the headliner for all cabin top winches and clutches. I believe Cal used the same hardware on the 28-2's as they did on the 33-2's, so a lot of it's a bit over sized for a 28 footer.
We looked at every Cal 28-2 that we could prior to purchasing ours (probably 6 or 7). At the time (Fall '09), I'd seen recent surveys on 4 different hulls (including our own survey).
In addition to what you'd expect after 25 years, here are 4 consistent observations common to just about all the boats we looked at. There may have been more, but time's starting to work on my memory.
1. The fabric liner in the very aft section of the quarter berth usually showed some sign of previous water intrusion. Ours does not leak but there is some streaking evident from a past event.
2. Evidence of water leaking onto the quarter berth cushion closest to center line. Probably due to either the quarter berth port light (opening into cockpit) or the pedestal feet. On ours it was the pedestal feet, rebedding corrected issue.
3. Aft Sbd teak toe rail was checked/cracked on about half the boats (about 1/2 the boats)
4. Visible Keel/Hull joint on 3 of the boats (2 we saw ourselves, another was observed and noted in the survey).
In '88 and '89 (maybe late '87 too), Cal used an 18HP Yanmar and installed an additional opening port light in the quarter berth. Nice options if you had a choice to pick from.
I have tons of pictures from all sorts of boats if you need a better look at anything. Good luck, they're nice boats but I'm a bit a bit biased.