technically... you can make a region any size you want (UNCHECK snap-to-grid).. BUT, you'd end up with weird aspect ratio issues

personally, i find it easier to stack the clones on the right or left... that way my eyes only go to one area.

let's say you want to stack them on the right... but you need to keep the aspect ratio the same... the problem is figuring out the size of the small ones and the big on. here is the math:

W == screen horizontal resolution
H == screen vertical resolution
cx = region width
cy = region height
N = number of wows total (small and large)

cy = H / (N - 1) <-- assuming 1 large region and the rest stacked

(W - cx) / H = cx / cy

(W - cx) = H * cx / cy

since cy = H / (N - 1)

(W - cx) = H * cx * (N - 1) / H
or
(W - cx) = cx * (N - 1)


which simplifies to:

W = N * cx

cx = W / N

so, if you want 1 large w/ 4 stack on 1280x1024 ...
cy == (1024/4) == 256
cx = 1280/5 == 256

so your small regions are all 256x256 and your big region is 1024 x 1024

give it a try and let me know how it goes. btw, you can enter the dimensions directly into the fields.. just don't put any spaces and separate numbers by a comma