looks like how I ran 3 boxing for about a month before I figured this out. There isn't much of a formula, just playing with a calculator till you're close.
Currently you have
1650/700 = 2.357
550/350=1.57

with a 1650x1050 monitor, stacked like that,

Set your big window to 1650x785= 2.10
set your small windows to 550x265 = 2.07
and run 1650x785 resolution.


should be a lot closer

Another option I ran with for a while is stacking the 3 down the side, but I don't have a widescreen monitor, so I kinda missed out on my "peripheral"vision because my windows were almost taller than wide. But for 5 boxing, that's exactly what I do, the 4 down the side, and then when I'm only playing 4, I just leave a hole where the one I don't open should be. If you wanna play with it, it could work.