Emiliano & Richard:

I can't dedicate a layer out of my 4 just for pixelmad as I need all 4 to generate my video output and so scaling in the layers is not an option as it'd affect the video out.

As Nev said, I'd like to use most of my main video output as the source for colorweb (minus a layer or two) and so it'd make sense to be able to simply scale a submix down to 20x16 with no cropping.

Nev's solution with keystone scale works absolutely perfectly. Thank you!

Sized the submix to 100x100 then scaled to 0.12 using keystone to get the size I need.

Saved me a few quid for this weekend anyway, Cheers Nev.