I decided to add shocks to my 31RLD TT after travelling some of our finer Interstate highways (I86, I30, I40 to name a few).
I bought the Monroe kits but I had to do some jury rigging because the axles are below the springs and the kits are designed for axles that are above the springs. I could have mounted the new plate on top and gotten shorter shocks but I wanted as much travel in the shocks as possible.
I used the original plate where it was, on top of the springs, and used the new plate below the axle. I replaced the U bolts with 1/2' bolts & double nuts to secure the plates/axle/spring. I tightened the bolts just enough to put a slight bend in the new plates and added scrap shims between the axle and the bolts to insure there was no horizontal play between the axle and bolts.
I put the shocks through rubber roofing underlayment and taped it to the belly with eternabond tape to keep the integrity of the belly intact.
I have about 2500 miles on the rig since doing the mod with no problems whatever and there is an amazing difference in towing.