Ok this is starting to get embarrasing, but I'll fess up in the hopes it can save another servo sub builder some grief. As I've posted previously when I finally built H-frames (orginally had all the drivers in big flat baffles and firing forward) I originally just wired everything in a parallel manner. Sounded pretty good, but I wasn't getting the slam everyone was claiming. So after a post, Danny provided the wiring diagram for the V1. The parallel arrangement, especially for the servo coil was of course way wrong. So w/ a fix, a big improvement. (I know others have at least made this mistake)
However I noticed with one unit, the drivers would start to 'loose control' and start bottoming out when pushed even moderately hard. The other one was more robust. I've been pretty busy and just sort of ignored it. However last night I thought.....something has to be wrong w/ the wiring. I traced everything in the H-frame. All ok. Then I looked at the wiring harness. I had mistakenly ordered the dual harness, which I really didn't need. Just for the heck of it, I switched the servo leads from one set to the other.....an viola!. Now the drivers were locked into proper control. So apparently, I had no servo control before. The VC was driven by one side of the harness, and the servo was connected to the other.
While I've actually been preety pleased all along, now I'm realizing why this setup is truly something special.
So yes it's a sordid tale, but I hope it helps someone out there!