Mixing 1080/60i with 720/30p after converting all to AIC

Half my footage was shot at 1080/60i and the other half at 720/30p. The raw is all in mts. I am using FCP5 so I converted it all to AIC using clipwrap. I have been editing them in different projects with the audio/video setting under preferences set respectively. Now I want to combine my scenes on the same timeline... When I drag the 720 over to the 1080 the 720 looks reduced (because it's sitting in a 1080 canvas; I know) and vise versa.

I'm thinking:

1. I shrink all the 1080 to 720 using the image+wireframe?
2. I render my 1080 scenes to a native quicktime file and then convert that to 720 in compresor?

Or am I missing something really obvious?
Thanks a bunch!