Export half of screen area?

Hi all, I'm producing some very wide edits for a conference and the staging co have requested that the files be split L & R on top of each other on a 'carrier' size/format which they can play back and therefore keeps the quality high and sync.
They will, during playback, re composite the L&R using their on-site kit.
Q So is there a way to export part of the screen ie left side then right side which I can then re composite on the 'carrier'?

Info:
Final display size - 6720 x 1008
'Carrier' size - 3840 x 2160

Last year when we did the job the screen had a lower pixel count, same general proportion, so I produced 3840 x 500 approx files which looked fine. Also all footage was HD rather than 4k and we had multiple images across the the screen.

Many thanks

Right off the top of my head, I'd put the whole Timeline into a Compound Clip.
Then mane a L-Timeline and an R-TImeline.
Each of these projects would be the frame size of half, as needed for output.
Place the CC in each, reposition so they're left and right sides.
Export.

If they need full frame size, but only left an right halves showing, duplicate your exciting project, Crop each to show only half.

But, I'm not 100% clear what is needed, so this may be off target.

Hi FCPX guru, I can see your logical thinking thanks. So if I set up the final delivery/carrier project (3840 x 2160 which is 4K) than as you suggest comp clip, drop into the top half the left side and the bottom half the right side then export the 4K file. As I will have a lot to export like this I'm assuming that once I get one done I can then drag drop and replace the content with the 4k carrier?

Many thanks

Sure, why not? What's the worst that could happen? We all die. So what, some of us are too old anyway. Try it out, see how it works. I ain't scared!

I'd do it, see what you end up with, see what the client says. If it needs a tweak, not a problem, eh?