What stops you from trying it? That is your best answer, but first update to 4.2
Why would 4.2 add more frame rates, it doesn't.
I tried editing a preset file from mdia encoder - frame rate line, but it still ends up at 30 (it displays "40." in the preview window and 1 in the drop-down) as suggested here > 40fps timebase in premier 7 pro ? - Video Editing Forums: Digital ...
But that didn't work so I'm out of ideas.
Why don't you use 50 fps, that is possible with a desktop sequence. 4.0 has a lot more problems and less features and stability than 4.2.
50 is uneven, my 30fps footage ends up getting gaps in it, and I cant even drag it evenly together, I have to move the entire sequence ahead/behind a portion to make up for the uneven timeline...that's if I work in 50fps.
But filesize 40 vs 50fps comes in to proportion as well.
You can't do that in Pr. Try VirtualDub. It's free, and part of what I consider to be an essential toolkit of open-source applications to complement Pr.
I always render out with lagarith (next to lossless) and encode in x264.
Think it's possible to render out 60fps and set x264 to 40fps or will it go out of sync?