Boubou - I agree with Diesel Donnie that you should have a minimum of 5 inches clearance above your TV bed rails, but IMHO, six would be better. An example would be the CG I just spent a week in, which had a railroad track crossing the entrance road. The track was about 3 feet higher than the road, with very short ramps up and down. When I went over it with my 33' 5er, the bed rails cleared by less than 1/2 inch, and I have 6 inches of clearance. 5 inches clearance would have bottomed on the bed rails. 5 inches would work most of the time, but you never know when you will encounter a need for more clearance.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.