Brion/Ian,
You are correct, the stays are 3/16 and I'm not able to make any adjustments to the location of the upper chainplates.
Since the mast is down for the winter, I'm unable to site up the shrouds but I was able to locate a side picture (and I highlighted the stays for better visiblity). Although it appears that the upper's are fairly straight from deck to masthead, it's now easier for me to visualize the problem that you (both) pointed out and how I might be having a problem. If I correctly understand Ian, once tension is applied on the shrouds, the shrouds will force the spreaders to "find" its angle, either fore or aft and by the signs on the spreader base, it appears that the spreaders are being forced forward resulting in the spreaders not being able to introduce pre-bend.
Just to recap:
Even though I'm following Catalina's spec's on loading to the tee, I'm thinking that I have too much tension on the lowers which is not allowing the mast to flex and it's forcing the spreaders forward. This should be a easy correction/fix.
It now appears that I do have a problem with the spreader base from the inboard edges, to the wallowing of the clevis pin holes from years of wear. Fixing the pin holes should be straight forward but how do I ever determine the proper angle of spreaders? Or by Ian's comments, should I expect to see some swing (of the spreaders) to the aft as I tighten the shrouds but try to control any forward movement? It just seems like a delicate balancing act with swept back spreaders.
