360° video within a multicam clip

Follow me here.

I recorded a live event with traditional 1080p cameras and also with a 360° camera (2560x1280), with the intention of being able to edit a separate version of the 1080p version and the 360° version.

I got all cameras imported, put into a multicam clip, synced up, then brought the multicam clip into a new 1080p project, and started doing lots of edits and cuts. (I had to chop a lot of dead space within the live event.)

The 1080p project is fine.

Then I duplicated the 1080p project to start working on the 360° version. Once in the 360° version, I switched all the camera angles to the 360° camera, which worked fine.

However, FCPX doesn't appear to let me recognize the 360° project as being in 360°. In the project properties, I specified the custom video size (2560x1280), but projection type is grayed out, so I can't tell FCPX that this project is a 360° video.

Is that a bug/oversight?

I really don't want to have to duplicate all my painstaking work in cutting dead space out of the live event. I was hoping the edits I made in the 1080p event would easily translate over to the 360° event.

Is there a way to create this 360° version, without having to re-edit it from scratch?

Thanks!