Its a clunky work around but you could export just the joined clips back out to the DV camera, and then re-import as one clip. As the DV files are not lossy, this should keep the original quality while acheiving what you want.
Like I said it s not the best, but you could separate your project into several runs to be exported to camera as an additional step in pre-production. Reimport in the x number of import sessions, effectively gluing the clips together. This time when you import, Imovie should not separate them like it does when there are pauses in the original recording. Obviously you still maintain the 9.x minute clip length limit, but its better than nothing. Unfortunately, I don't know an elegant solution to your problem
