A couple ideas. Not sure if you have Arena and can do some advanced output config. But that is one option.
Maybe a simpler option is to not focus on the shape. What I see is a full size layer in the back. Then a scaled down layer in front of it. So your Video Loops would go on the bottom layer. Then the layer 2 would be scaled down, and the Y position adjusted to align with the bottom of the screen. That way all clips in Layer 2 will play at that scale and location.
Win 10 pro 64 bit - b1809 - 2.7ghz i7, 16 gig, 3 SSD internal drives
NVIDIA 870m v 418.91
Resolume Arena 6.12 & Akai APC40 MKII
Virtual DJ 8 & NS7 III (video DJ)
Ableton Live 10