Sync Bin and multiple files from one camera DR17

I am trying to sync ~70m of video from two cameras in DaVinci Resolve 17. The first camera produced a single file. The second truncates files at ~30m and so has three files.
Initially I tried Sync Clips with the four individual files. It created 4 separate camera angles. Audio sync is not possible. I tried In markers, but this doesn't really make sense for the three time split files from the one camera, and manual sync to frame accuracy is almost impossible with the clips on different cameras rather than the one, and there don't seem to be any zoom controls or ways to jog a clip left or right relative to the others.
I then tried creating a compound clip of the three files from the second camera, but Sync Clips ignores the compound clip and only adds the file from the other camera to the sync group.
After more googling I edited the camera metadata of the files so the three time split clips had the same camera ID, and made them camera 2. Likewise for the other camera, it was marked as camera 1. Sync Clips then recognised only two cameras (good) but only the first of the three clips from camera 2 was added to the sync group and the other two are ignored.
Surely this can be done. I really want to use the SyncBin, but this feels like I've run into a brick wall. Has anyone tackled this? Or can provide the exact Blackmagic metadata incantation required to achieve what should be a fairly simple task?
Thanks
Initially I tried Sync Clips with the four individual files. It created 4 separate camera angles. Audio sync is not possible. I tried In markers, but this doesn't really make sense for the three time split files from the one camera, and manual sync to frame accuracy is almost impossible with the clips on different cameras rather than the one, and there don't seem to be any zoom controls or ways to jog a clip left or right relative to the others.
I then tried creating a compound clip of the three files from the second camera, but Sync Clips ignores the compound clip and only adds the file from the other camera to the sync group.
After more googling I edited the camera metadata of the files so the three time split clips had the same camera ID, and made them camera 2. Likewise for the other camera, it was marked as camera 1. Sync Clips then recognised only two cameras (good) but only the first of the three clips from camera 2 was added to the sync group and the other two are ignored.
Surely this can be done. I really want to use the SyncBin, but this feels like I've run into a brick wall. Has anyone tackled this? Or can provide the exact Blackmagic metadata incantation required to achieve what should be a fairly simple task?
Thanks