Well, I'm happy to report that by using the service menu (D-CONV) I was able to tweak out some annoying convergence on the left side of my newly acquired 30XS955. It's not perfect, but significantly better.
I also had a go at trying to reduce the overscan. My results were mixed. I was totally able to optimize it for an Xbox set to 16:9 mode. (I compared it to my projector at 0% overscan - very close.) However, that resulted in widescreen output from a PS2 being too small with the sides of the image itself visible. So I had to compromise and increase the HSIZ and VSIZ again slightly so both would be OK.
I expect I'll have to adjust this again when I finally hook up an Xbox 360 to the set. I've heard that I might have to use the MID3 group to adjust 1080 input. (By the way, is there no way to see what the input signal format is other than being in the service menu?)
I was really glad I could adjust out that convergence error. All this is a bit more inconsistent and finicky than my 1280x720 projector, but hey this is about as good as it can get on a CRT (TV) as I understand it, so I can "put up" with small issues.
One thing I'm worried about is whether or not I have maintained a correct aspect after playing with HSIZ and VSIZ - that is, I hope circles are still truly circular! It looks fine, but I haven't measured it yet. Part of the problem is that the DVD playback from PS2 is weird. I put the THX optomizer in there from a movie and could not get the circle in the widescreen check to be circular. For some reason it was still letterboxing in my 16:9 screen - lame. Game material does not look stretched or squished (I didn't try the actual movie).
One thing I noticed last night is when I changed a PS2 game to run progressive (there are a few) the image shifted to the right so now I have a small gap of black on the left side...huh? (I was not in the service menu - no other changes than going from 480i to 480p.) This did bug me - any ideas?
Well, I'm not intending to tweak forever (addicting as it is) but sometimes I just don't get why the image is so inconsistent across inputs/sources/formats. (All the above is on component connections via inputs 5 and 6.)
I labeled PS2 input 5 "Beta" just to give Sony props (and because, yes, I actually was a Beta user...)