The way I personally like to deal with situations like this is to use dummy mixes for masking, the cost for your situation would be 2 mixes(background transparent, Keystone mix type) and 1 layer(set to black scaled as large as possible and routed to the 2 mixes).

If you have line of sight with your screens from your HUD its a 30 second job and then save preferences. Or you can use the web interface as you have full mix controls there for the keystoning, its only numeric but you can either type hard values or scrub your mouse to find the sweet spot, and that should be a quick solution once you get upto speed with x1 x2 etc.

For daily masks I prefer to use mixes that are set on the show machine with uppermost priority as there no chance of a programming related mistake happening, your masks will ALWAYS uppermost, and you can always change content without concerning yourself with the masking on a certain layer.

Phil
Philip G Haynes
Live Visual Design and Direction