Hello Vern, welcome to irv2.com! Reese Products
recommends a minimum of 6 inches clearance between truck-bed sides and the bottom of your 5er overshot. That is my minimum, and I've gotten a scare about every trip.
When/if your 5er makes contact with your truck-bed, you will have damage, how much depends on your reaction speed.
If you plan to tow your 5er to back-country campsites, I suggest you raise your 5er to obtain about 8 inches minimum clearance. This may require re-positioning the 5er axles to under the springs in order to maintain a level towing stance.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA." My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy