[Corrado Magalotti] “BTW No way to start a clip on a specific frame?”
Two ways that I know of. Either drop the clip into the dropzone and then ALT-drag until the frame you want is at the head, or edit the clip in FCP so that it starts and ends exactly where you want it to, export and reimport it, and drop that into the dropzone.
EDIT – I’ve just had a play in Motion 4 and you can also just add the original full-length clip to the dropzone and then trim the dropzone in the timeline or mini-timeline so that it starts and ends where you want it to.