Thanks, but nope. I'm already making use of the scaling options in project settings.
The thing is that while you can set your game resolution to scale up to fill the screen, the screen will always be set to the target device's native resolution. On PC's and Mac's, if the desktop resolution is 1900x1200 then a game resolution of 400x300 gets scaled four times with letterbox scale. That's fine, except 4x4 scale seems to suck up a *lot* more gpu power than 1x1 or 2x2 scale for some reason, even with webgl enabled.
I've tested on a Geforce GT 540M and a Geforce 9500, and performance drops to something like 10-20 fps on both of em if the desktop resolution goes beyond the 1280x960 range. These aren't the beefiest gpu's around, but they're not feeble either. If they can render a game resolution of 400x300 fine at 1024x768 desktop resolution, then they should be able to do the same at 1600x1200, no?