I thought I would close the loop on this issue. After much research and analysis, I decided to go with a pair of "airless" Sumo Springs #SSR - 114-54. These proprietary, 2800 lbs. rated, 5" closed cell, urethane jounce (bump) stops replace the OEM 3" 'ish bump stops. They do not touching when we unload the truck camper so unloaded ride quality is unaffected. The Sumo's leave about an inch air gap when the truck is unloaded ... which is why they have no effect on the original, unloaded ride quality.
SuperSprings tag line for these Sumo Springs is "fit and forget them". This appealed to me as I did not want to install a more costly and complicated air bag system. My decision to go with the Sumo's was based on a number of factors including input from various "experts" that sell and install them, cost, no maintenance, controlling sway & porpoising, increasing load capacity (not "legal" rated capacity) and lifting the sagging back end when loaded with our truck camper.
Total cost was $235 for the product with an all in price of USD $350 including installation labour and tax. I had the work completed at Michigan Truck Springs in Saginaw MI and have nothing but good things to say about their price, service and approach. They are supposed to take about an hour to install but the shop worked on them for about 2.5 hours. I suspect being a truck from the saltbelt had a lot to do with having a tough time loosening the original hardware which probably hadn't been touched since new (15 years).
We immediately noticed the truck sat higher in the rear when they brought it around to the Service Reception area. A rough measurement said it raised the back end around 2" .... which means our sag is only 1.5" now when fully loaded with truck camper and cargo trailer. The truck definitely rode firmer, not harshly, just more solidly with noticeably much less sway. An initial negative was it made all kinds of weird suspension noises for about the first 30 minutes when we started driving. We decided this was because the rub points and angles had changed and mechanical bits were now touching in a way that they weren't touching before. Sure enough, after about an hour of driving, all "new" noises disappeared.
When fully loaded, our truck sits on the Sumo Springs which is fine because there is no "slapping" or "banging" action to create noise or an uncomfortable ride. I also noticed our overload spring bump stops were now only lightly engaged with the new Sumo setup as opposed to before when they were fully engaged and the overloads partially flattened. This tells me these things really do help with load capacity.
Bottom Line - if you read my original post and the problems I was trying to fix, these Sumo Springs did exactly what I wanted and performed as advertised. I am now a very "happy camper" with this setup.
