I am no expert on the matter, but if the smaller wires are running hotter, then that heat is drawing power from somewhere. I should think that the smaller wires will run hot, with increased resistance, less juice to the lights AND more draw on the battery.
I set my regulator for a little over 9 volts, but I tried not to run much over that to let the bulbs last a little longer.
Another thing to consider, Turkey, is that there is a chance that the guy who tweaked your regulator mis-tweaked the cutout relay at the same time, so that the generator drains the battery at idle. It might not be a bad idea to have someone you know to be competent look over the whole charging system.
I wish I had found this site before I did the 8-volt shift on my own truck, but it works just fine at the moment. I'll be going back to 6-volt when this battery dies.

It may not be the easy way, but it is the Cowboy Way - Ranger Doug
Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri
1953 Chevy 3100
1960 Volvo PV 544
1941 Chevrolet Special Deluxe