My Stable Loads clearance is about 1/2 inch rr, and 1/4" frnt. above the secondaries when the truck is empty. A little bump is O.K. A big bump and it is jarring. With the camper on and loaded the 3 secondaries settle right on the Sta. Lds. and settle all the springs a bit, but not close to bottoming out on the lower overload spring. Tomorrow I'll put the add-a-leaf at the bottom of the main spring pack and see where everything lands. I'm ready to trim the Sta. Lds. if necessary.
In your case, do some experimenting. You want the better unloaded ride you get with the stock springs and no secondaries or air bags in play (of course with a minimum inflation), but the rather even load distribution on all the leaf springs you get with the TC on. It sounds to me like your upper secondaries will take less of the load than the main spring pack than they should with that 1-1/2 inch gap at unloaded. If you inflate the air bags to level the ride you may lift the upper over loads right out of the picture, negating the less-rebounding ride you get with an even load on all the springs and not a lot of air in the air bags. You will find out soon enough.
Every single rig has it's own 'quality' of spring sets, even among the same make and model. Yes, i think some incremental experimentation is in your future
Here's the 'before' on my rear suspension:
That black block is the rr Stable Load with about 1/2" clearance.
Here is the frnt. dr. side Sta. Ld. with about 1/4" clearance.
regards, as always, jefe
'01.5 Dodge 2500 4x4, CTD, Qcab, SB, NV5600, 241HD, 4.10's, Dana 70/TruTrac; Dana 80/ TruTrac, Spintec hub conversion, H.D. susp, 315/75R16's on 7.5" and 10" wide steel wheels, Vulcan big line, Warn M15K winch '98 Lance Lite 165s, 8' 6" X-cab, 200w Solar