So I want to film at 4k @ 24fps for Max Quality but also want to be able to have some slow mo shots. Help! It's confusing, I'd rather not be switching between frame rates and switching to 1080p at 60fps when I think I may want slow mo. So can I film everything in 4k @24mpd to get Max image quality and then use optical flow in FCP X? or will it just look like crap? 

What's the best way to do it?