Truck Toppers, Bed Movement, and Cap Gaps

[bigmistake]

I recently picked up a truck topper for my MJ - it isn't Comanche specific, so it doesn't fit perfect.

 

I was wondering how close the topper can be to the cab without causing issues?  I know there is a gap between the cab and cap on most trucks, but since our trucks are unibody, does the bed ever move independently of the cab?

 

Thanks!

[Jeep Driver]

The bed is independent of the cab. 

 

Everything flexes. 

[masimmons25]

Anyone ever measure the deflection of the rear frame and bed relative to the cab under flex?

[gogmorgo]

Good luck finding that info. 

The MJ is a ton more rigid than competing light trucks from the era, but there's still some. I initially had my Leer topper about an inch from my cab, and never made contact, but I wasn't wheeling it. Eventually I moved it back a touch so I could get my hand back there from the outside to unlatch the pass-through window to the topper, so I could open that and juggle the MJ's slider window open in the event I locked myself out.