Would it be useful to run a grounding strap from the rear underside of the car to the front (attaching it to the unibody along the way)? Would this improve the ground performance over the entire body for such issues as dim lights or intermittent faults?

It seems that every electrical problem with my Z has been resolved by either putting in a better grounding strap or tightening the original one. I would suggest you locate every last one of your grounding locations and make sure it ready is a good ground (connection is tight, nut/bolt not rusty, wires in good shape) then tighten. Add a 8 gauge strap from the engine to the frame and you should be fine. Remember that there are several grounding locations on the frame (fuel pump- electric if you have one, lights, wiring harness along passenger side, lights, horns, etc) and may in the interior (the center console has at least one major one). I don't know what you do for a living but whatever it is you can't afford to pay some one to do this (I worked for over 40 hrs finding 2 bad connections in the dash. At $50/hr that'd be $2,000. just to fix a grounding issue). Get a test light and voltmeter and practice getting flexible since you'll be twisting yourself into small places under the dash, etc. A small foam pad is good for your knees. Good Luck......be there and done that.

Welcome GnoseZ, I noticed post # was low. I like your line of thought. Look forward to more.

Been over at zcar for some time but have grown tired of the lack of civility, decorum, etc. SilverBullet highly recommended this site and I've been on for a short while mostly reading old posts and learning. If a little knowledge is dangerous then I'm a little dangerous....