I normally suggest to refrain from making larger skin sizes, but it's up to you.. I know for a fact that in some systems, the high-load of memory will prevent a lot of screens from being loaded at once which will force you to limit the number of screens that RR can have loaded, and make you re-load screens (taking up performance).. I myself never had that issue, but Chuck can probably give you plenty of details about it (he's made a 1280x1024 skin I think)..
thanks for this breif and precise answer.
I'm also trying mo modify the 800x600
skins the hard way until i saw your reply
and tried it! it works on my 15" 1024x768
screen! I owe you one coz you save me
a lot of time!