I've tried 4 on both 1680x1050 (20-22" widescreen) and 1920x1200 (24" widescreen), and it would be very difficult to have a window much smaller than my 1680x1050 alts (840x525). If you're going with a 17"-19" widescreen (1440x900), the windows are going to be tiny. You could do 480x900 x3 to have 3 equal windows horizontally.. or split it in half horizontally with two on top (1440x450 + 2x 720x450). I'd prefer to step up to a 22" 1680x1050 or 24" 1920x1200 and split that 3 ways.. 640x1200 x3 would be alright.. a little narrow, but do-able. It doesn't take much time to set up once you have the monitors.. so you can try a few different ways to organize the windows. I'd just recomment going as large as you can afford for alts since you want to put more than 2 windows on one display.