Thanks for the response.
I was missing one or two things in my xorg.conf so the display was not totally stable (glitches in the sync). With a new mode line: 'Modeline "1600x1200-reduced-blank" 130.25 1600 1648 1680 1760 1200 1203 1207 1235 +hsync -vsync' and possibly the option 'Option "ExactModeTimingsDVI" "yes"' for the nvidia driver, it now seems that the display is glitch-free. I found there is another thread about reduced blanking on DVI in this forum: http://www.nvnews.net/vbulletin/showthread.php?t=52052
The VESA xls was helpful.
Haven't tried it on 10.1 yet. I suspect that the problem I saw on 10.1 was caused by a combination of an USB mouse and what appears to be somewhat flaky USB on my MOBO. I have now converted to PS/2 mouse.