Ackkk, well, I spoke too soon.
I was checking my tweak at various points of reassembly, and I thought it was fine... then today I just went down to finish it all up. Soldered in my electronics, check all my shocks, reset them all to exactly the same preload (well, same # of turns anyway) and set my downstops before I put the shocks and tires back on so I could continue setup. Set my front to 6mm and rear to 5mm as per the standard setup sheet. Threw the shocks on, threw the tires on and checked the balance of the car. It was slightly heavy on my battery side (7000 mah ready = heavy) so I put weights on the other side one at a time until the balance seemed good. Then went to set my ride height and noticed I had to crank the same two (opposite) shocks to get the ride height correct and new right away the tweak was back. Sure enough I checked it and it is out, in the same orientation as before.
So, I guess it comes down to weight balance on the car. It might be extreme, but I'm going to go pickup 4 kitchen scales and set the car on it and see how each corner looks for weight and move stuff around until they are as even as I can get em.
Does this sound reasonable, or am I missing something crucial?
Thanks again for all the help so far! Even though I'm having some bad luck here, I'm really enjoying the problem solving.
Luke