You are lining up one LL where you can choose the return time and one LL where you cannot, so that can make things a little tricky, but definitely not impossible. Personally, what I would do is this...at 7am select a late morning / early afternoon return time for FoP. Then refresh until Navi pushes out to an overlapping time and then book that one.
If you did attempt to book Navi first, then try to book FoP and it's already pushed out too late for them to overlap, you could always finish booking FoP, then cancel Navi and refresh until they do overlap.
You have some options!