You probably can use as many lights as you want with one thing in mind
Steve,
You can only have 4 bulbs lit at any one time on the front of a vehicle in Texas. The laws seem confusing, but I have had them "explained" to me twice by TDPS officers.
In Texas, you also cannot have fog lights on at the same time as your brights, although I don't know how they would notice this (how could they tell they weren't driving lights?). I have an extra pair of fog lights that I use with my brights.
May see you out in W TX this May/June. I'll be the one with only 4 lights burning and fog lights on under my brights LOL.
Chris
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Chris Harrison