I mounted 4 lights, but used 35watt PIAA brand fog lights becuase I didn't want to overtax the electrical system. I also have a factory supplied 55watt rear facing aux light on the rear bumper. When using the rear facing lights, I light up the 2 rear lights on the ROPS plus the factory rear aux light. When mowing in the evenings, I use the front facing 2 lights on the ROPS. You can draw down your battery if your alternator isn't up to the task of recharging the system. So under the worst situation, I run 3 lights (1x55 watts + 2x35 watts).
As far as warrenty, there is debate to drilling & welding the ROPS. Generally put, some people don't care, others are totally **** about it. I live on hills so I didn't want to risk anything. There is also a future liability issue, again some don't care, others are **** about it. But in theory, if you weld or drill your ROPS, and someone else is using your tractor, or you sell your tractor, and they are injured, then they can sue you.
What I do know for fact is that the ONE TIME that I almost flipped my tractor it was when I was using the FEL and working on flat smooth asphalt and not even messing with the hills. So I guess NOW it would be safe to say that I fall into the **** category of drilling & welding. Before my near roll, I would have been an advocate of not drilling or welding, but that was because of my fear of rolling on the hills. When I learned that tractors can be just as dangerous on FLAT land is when I decided that I would not risk my life or my family's future just because it would be easier to drill into my ROPS. JMHO.
The angle iron I used was about 20" long and I got it for free. The 2 part marine epoxy cost me about $6 or $7. A can of black spray paint set me back about $3. The epoxy took overnight to set up. So for my efforts, I spent about $10, and I clamped the angle iron ot the ROPS one evening, hung the lights the next day. Not too much expense or grief to eliminate the warrenty & liability issues and to keep my piece of mind.