I thought I'd update this suspension thread now that we have about 4800 miles on the changes. It's been a good test as I sometimes think our travel route is more of a tour of every crap road out there.
Pic below is in Palo Duro Canyon, TX, our last stop on the way home to SE Texas. Beautiful.
Cliff Note - all in all, an excellent upgrade, big difference in the long daily travel drives. Note that bumps ARE felt, it's a tubby 10k lb. van with stiff suspension and 10 ply tires inflated per capacity spec, but the bumps are dealt with in a very controllable manner. No surprises. As a reminder, per CAT scales, front is 3720#, rear is 5700# with full travel load.
Our last trip leg heading back home we dealt with 20-25mph crosswinds. All day

very tiring to hold the ship steady hour after hour. But I can say that even with some of the WHOA gusts that hit us, the corrections needed were controllable and didn't result in a seesaw reaction as they did before.
Not too scientific personal observations....
Front Suspension
The new springs have settled at about 36 in, right at about a 2 in height increase from the stock (overloaded) springs. I think that the combination of the new coil springs and the black Sumo Springs has provided the suspension travel and control that was lacking. In hindsight, I think that I could simply have ground the top coil as a flat, about .5 in worth and that would have worked fine. But I'm very pleased with the front end performance.
Rear Suspension
Happy with this as well. I know that the big overload can be removed, but just my preference, I left it in place. The airbags are a great addition and have performed very well. One issue that came up was a slow leak that developed at one of the bag fittings, easily fixed by re-taping the fitting and re-tightening. I noticed that both fittings tended to loosen up a bit, so something to check. I run a separate line to each air bag.
The new u-bolts have settled in at a consistent 130 ft lbs., checked with a torque wrench along the way.
The sweet spot for us is a fender lip height of 37.5 in, or about 21 in from the top of the wheel center cap to the fender lip. This equates to anywhere from 40-55 psi in the bags depending on load. It's simpler for me to just get the fender lip height set rather than go with psi settings. This height/psi easily accommodates bumps and dips. Sometimes we do hit a very large unwelcome dip or bump, we definitely feel that impact but we don't go flying around everywhere as we did before.
Tires
This isn't about any particular brand but more about the speed rating and temperature/pressure rise I've observed. Before we left on this last trip I bought 2 new tires to replace date code 2015 tires. We had already replaced 2 tires about a year ago, so we essentially now had a new set of tires. Brand new tires (120R) were placed on the back and the almost-new tires (120Q) were moved to the front. They are 2 different brands, similar tread pattern, good quality. What I noticed was that the pressure rise with the new R rated tires was less than it had been with the Q rated tires, even though it's a very small difference in speed rating (99 mph vs 106 mph). I wonder though, if there's some sort of exponential construction difference needed at that fairly high speed, meaning that heat will build rapidly. The Q rated front tires would increase by 8-9 psi, and the R rated rear tires increased by no more than 5 psi. Just an observation.
Hub Temps
Hub temps generally ran in the 105-115d range. I noticed that the rear hubs (semi-floater) tended to stay in the 105-110d range. I'm aware of the tendency to eat hubs with the higher offset AR wheels and I'm going to grease the front hubs per the method that Booster describes.
On the rears, I think that proper fill level in the differential is key not only for axle bearing lubrication but for cooling as well. Many folks seldom check or change that fluid and quite often it gets low. As it gets lower there's less of it to get into the axle tubes and the end bearings. Less lube = hotter bearings and possible early failure, especially since they see a substantial load with these vans. My personal preference is Redline synthetic, and I typically change that fluid much more frequently than 100k miles. In general I regard changing of all fluids and filters as cheap insurance in the long run.
Future Musings
I'm considering the addition of a rear swaybar. I do like the version that Booster made and am thinking of duplicating that fabrication vs buying the (what I consider expensive) Roadmaster bar that clears the genset. I'll note that the front swaybar has already had all poly bushings/endlinks installed.
I've also talked with the truck suspension shop that installed the front coil springs about installing a dual rear wheel axle from an Express cargo vehicle. This is just in the "thinking about it" stage and I will need to take measurements and do some research, but I think this will help stability quite a bit. I'm able to fabricate and paint small fiberglass fender flares if needed so it's all legal and looks nice. If feasible that's a post for another day.
So again, in my opinion for a 210, changing out the front coils, adding Sumos and adding the 5K capacity airbags is one of the best upgrades you can do. And I think that combining with removal of the heavy overload spring yields even a more compliant ride as others have found.