Hi Trevor,
Thanks for your reply. I decided to go with your approach, though I found that the iphone footage didn’t need to scaled up with the motion tab since it already filled up the whole screen (except the pillarboxed part on the sides). I still have to render the iphone footage on the timeline, but I decided to live with that since the final product will only be a couple minutes total. I’m not sure if this has to do with the way I transcoded it (in MPEG Streamclip), but regardless I figured I’d just share my experience in case anyone else is in a similar situation.
Best,
Eve