I don't see the advantage of relays when there's no significant voltage drop and even then... but that's another subject. I'd try just a 55/60 Watts H4 halogen in an appropiate reflector (Cibié, Hella, Bosch, Marchal)*. My friend on her CB350F never encountered too much draw, but she didn't use her bike for rides around town ofcourse and her model had 21 watts indicator bulbs (18 watts is also good, you won't see the difference. Mind you, the indicators on the CB350F for France even had 10 watts bulbs!). If you're still worried about the draw, consider the Philips Ecovision H4. In tests it gave a better light than an ordinary 55/60 Watts halogen, it saves 20% consumption (so expect 44/48 Watts) and they're longlife too. Excellent choice.
*The European reflectors usually have an extra socket where you can fit a Ba9s bulb. I replaced the original 4w by a 20 watts halogen and use that as DRL.