When we brought bikes with our Coleman Bayside popup I used a bike rack on the back of my Explorer (this was pre-Expeditions). I "think" it clamped to the tow bar of the trailer hitch. It did cut the turning radius of the rig.
Roof storage on a popup is a good way to (1) overload the trailer and (2) damage the roof. While some have cross bars there is typically little available carrying capacity in the tires. Roof storage on top of an Expedition seems like it would require a forklift to bet anything up there and back down.
Rent kayaks. My adult daughter was crying for one and my wife came close to buying one for her and another for her husband. Moms will always be Moms!
A couple years ago a nice used kayak appeared on a local list and my daughter wanted me to transport it home with my Expedition. No way we could get it on the roof. Put all the seats down and and stuck it in the back. Maybe a 30 minute drive...
May 2018. Kayak has been used two (2) times since she bought it. Stays on a rack at the lake. Rent them as you need them!
-- Chuck