Note, if you have a P timeline, and export to I, all will look (and be) P, but the container is I. Nothing will change to the footage. This is totally acceptable! (Remember, in the old days all commercials were shot on 35 mm.)
Now if your cam originals are P, but your timeline is I, only stuff like moving graphics are different. (And smoother, better IMHO.)
This is also totally acceptable.
So, it’s not that hard. If it looks good, it is good.
Bouke
http://www.videotoolshed.com