Maybe I'm not quite getting what you want - I judge that you, in effect, need to have full manual control of the frame area and then control the frame area size and position to allow you to manually adjust the portions of SD video you require to then produce an HD output - customised upscaling I suppose?
Using the PiP tracks with Maintain AR switched off allows extensive re-positioning, oversizing and, in effect, cropping/zooming of content. Would that not do what you require?
Cheers
Adrian
Life is really simple, but we insist on making it complicated. (see below)
Confucius
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