Normally when I hear the term "handles", it's referring to the portion of a video clip that has been trimmed up before the in point, and after the out point.
You just want to scale down a 1080 comp to fit properly in a 720 comp. Well, that's a piece o'cake! Nest the 1080 comp inside the 720 comp. Highlight the nested comp. You can go Layer>Scale>Fit to Comp or you can use the keyboard shortcut -- ctl-alt-f (win) or cmd-opt-f (mac).
That's all there is to it.
I think you're my hero right now, but for future reference . . . I found the pathway solution as follows
Layer>TRANSFORM>Fit to Comp
Layer>SCALE - did not provide any Fit to Comp option so I nearly lost hope.
Now I just have to figure out how to get nested comps into PP, as opposed to AE named projects and I'm good to go. I have hundreds of lower thirds with code numerical names and I'm not sure how this impacts workflow.
Thank you . . .
Personally I would just leave everything 1080 and just set the output module to 720. You will get the same quality with a small fraction of the work.
I can't find "output module" but if I'm not going to "output" - can that work? I just use the AE Comp as is brought into PP and layered on top of video.
You can automatically scale to fit any asset in Premiere Pro including a dynamically linked AE composition.
You can also scale to fit horizontally (much better than scale to fit and safer to) any comp that is nested in another comp. Resizing all of the elements separately is, pardon my colloquialism, "nuts"…