set up the RS Hi&Lo beams on a dual relay 15 years ago - still going strong.
I note youu have a ? for the fuse amperage, simple way to work out the amps load:-
Watts/Volts=Amps
For example a set of 100 watt spotlights would be;
(100x2)watts/12volts = 16amps load
Cheers
James