Still Dimming

[gckless 5,000+ posts]

Planned to today alas rain. Might need to wait until tomorrow as I'm not going to peg the DBs in my garage.

That's fine. And realize that the problem you are describing is something wrong regardless if you have a system in there or not. Even if you disconnected all the amps in your system, this problem would still be there, and is why we are telling you wiring or components (alternator, voltage regulator, possibly battery) up front. You understand where this problem lies, and why?