Try this again. First response got clobbered. Seems to happen a
lot lately.
I use 55W halogens with out a problem. I only use two at a time. But, can turn on all four if I move the light switch half way between bright and dim.
Use a digital multi meter and aligator clips.
With the
Engine at idle measure your voltage.
Turn on one pair and make note of any voltage drop.
Turn on the next pair and also make note of any voltage drop.
Leave them on and at idle for 5 or ten minutes. Is the voltage steady flat or dropping.
Then take it for a ride with the light son and see if the voltage level recovers.
If it doesn't continue to drop then your fine.
Ideally you would want to measure the current flow by measuring the voltage across a fixed shunt. At idle and revs.
But, that is harder than guesstimating with the voltage level. Besides most people don't have the shunt or a high current meter. And it needs to be inline.