hi stroke and welcome to the forums!

if you'd like to correct the aspect ratio, try this (assuming your screen is 1280x1024):

region0: x,y: 0,0 w,h: 854,1024 (main area)
region1: x,y: 854,0 w,h: 426,512
region2: x,y: 854,512 w,h: 426,512

this should yield the same aspect ratio for all 3. (don't forget to turn off 'snap to grid')
ie:
854 / 1050 == 0.833
426 / 512 == 0.832

if so, please post an update to show the difference

(BTW, how do you like PiP?)