to continue on the last point there, yes IF you are interested in doing a hack of this nature mobile LCD's are probally the best bet, I used to work at a car audio WD and 7-10 inch screens were stocked at all times and were fairly inexpensive (less than 150$ for a 7 inch) as long as you didnt get into nice brands or "options"

some had (in addition to composite) RGB inputs (which its not that hard to take a vga style signal and time it down to rgb) and s-video, new models even had dvi and hdmi

course the biggest thing now is HD and WIDESCREEN, which sucks cause the old aspect ratios are not going to be made much longer, but at the moment there is probally enough overstock to drive prices down to cost

I also agree its better to get one larger than the opening or you will see the edges, I dont know about os 9-x but its pretty common to be able to adjust display settings to fit a screen regardless of resolution in linux, I do it often enough with sd tv's and hacked consoles running linux

if it wasnt for that fact I could not see the menubars in Xdsl while running the xbox, eventho the screen res is 640x480 its really running something like 548x360 or something totally off the wall to fit onto a tv with all of its overscan and imperfection