Guides, cropping, scaling and accurate video placement

Question

I'm disappointed with the apparent lack of tools to accurately place videos (pip) within a 1080p (or otherwise) sequence.
I have a 1080p sequence, and four 720p videos that I want to crop and then scale and position to fit each quadrant of the final video - each PiP would be exactly 960x540 pixels.
The crop effect is ok, but doesn't show you "pixel" units, only %. The Motion effect does show pixels but positions everything relative to the centre of the original video (after scaling)
I would have expected the crop effect to change the bounding box of the video and maybe the ability to precisely define the size in pixels and zoom in percentage but no....
Not that this matters of course because there are no "rulers" / "guides" or otherwise to snap to anyway so positioning would still be a pain.
According to similar posts on the forum you can make "image based transparent guides" but these don't offer the ability to snap videos in place either and I like being precise - dragging stuff around on the screen by eye doesn't fill me with warm fuzzy feelings.
I've worked around this issue using basic maths (essentially since I'm cropping to 1/2 the original videos dimensions I set the scale to 150% and just calculate the positional offsets using 1920*(0.5-%crop) and 1080*(0.5-%crop) and then adding multiples of 1920/2 and 1080/2 to define which quadrant I want the video in.
Surely there must be a better way, rather than resorting to pen and paper?

Answer 1

Then the track matte would come in.
With a matte you can pick out any section of the frame.
nest it.
Set anchor point exactly on the top left corner of the visibel frame.
Now you can positon the pip like in post 5.