Hey Barry - Sorry for the delayed response.
Here is a thread, and it has another embedded link to SS MCU's too.
If you are good with our coaches handling, leave well enough alone
! My DW is terrified of driving on mountain roads (According to her, it's always a 267,008 foot drop, no guard rails, and the passenger seat is cantilevered out over the abyss...). And as the S curves change from left to right back to left, etc., etc. - each time she is positive the shifting of weight from side to side is going to tip us over. (All kidding aside, it is the leaning towards the outside arc that gets to her the most.)
So I did a few things to be sure handling was as good as I could get it, short of Active Air
1) All axle alignment, which includes checking the road height
2) All bushings were checked for wear, and are in top shape
3) Four corner weight while loaded for travel, and tires manufactures recommended PSI. (+ 10% contingency so I don't need to top off air while traveling.)
4) Went with Road King Shocks in all positions. (If doing to day, I'd add Road Kings to the Steers, and Koni EVO 99's to the Rear and Tag. Or, to save a bit more, I believe 95% of coach owner's would be pleased with the Koni EVO 99's on the Steers, and Koni Adjustable SP3's on the Rear and Tag.)
5) I added SS MCU's and traveled with them for several years. They helped 'set' the coach faster. Not just in S curves, but in strong shifting cross wind change driving conditions - and I'm positive in a emergency maneuver too.
6) When I was talking with Source Engineering about the Thermal Wax Valve, we got to talking about the MCU's we had on. They offered me to try their Comfort Control Valves, and if I did not like them I could return them and I'd be able to put back on the SS MCU's. So I did, and the faster suspension 'setting' was the same. And the check valve only checking in one direction, adds zero stiffness to the ride over say expansion joints, DOT's, pot holes.
On a different answer, to one you asked on the Cummins section (That I just saw.), we've about 20K miles on our coach since installing the FASS pump.
Best to you and all,