We have that also...30" cabs on each end. I don't know what kind of mirrors you're doing over each sink. But if they're coming in from the wall a little...say two inches on each side, that's bringing your mirror width to 26". You may also want the lights to come in a little also. Personally, I'm doing double sconces over our sinks. I like the look this gives better and there's plenty of light with the other lighting in our bathroom. Some images for you to peruse:

Just to let everyone know, the link for this post has changed: I think you only need to use one plug at the outlet end. You can connect up several light fixtures one-to-the-other in a straight line using the direct connector that comes with each light fixture. If you have to angle to a corner cab, or insert lights into a cavity, you can still connect the lights to each other using their flexible connector. Call Pegasus Lighting Associates and they will help you if you give them your measurements. 1-800-392-4818. Here is a link that might be useful: Pegasus micro-fluroescent undercab lights New Link: www.pegasusassociates.com/MicrofluorescentT4.jsp Here is a link that might be useful: Pegasus Associates Lighting

"Can I change a 3 bulb vanity light base so that the light is going up instead of down? If I can do it---how?" The light fixture should be removable from the wall. Depends on the style, it may connect as a whole to the junction box behind it, or it may connect to a mounting bracket that is installed on the wall. If you know the model, you can find installation instructions on the manufacturer's web pages. IF the light is attached to the junction box, remove the light, rotate it 180 degrees, then reinstall. There should be no need to mess with the wiring. If there's a mounting bracket, the bracket may have a "this side up", or it might not. If not, detach the light from the bracket, rotate it 180 degrees, the reattach to the bracket. IF the bracket does have a "this side up" then drop the light, detach the bracket, rotate and reinstall, then reinstall the light. Prior to doing any work, turn the light switch off, and turn the breaker to that room off as well. You can lighten the load by taking the shades and bulbs off the fixture before working on it. "...or do I need an electrician to do it? " After you read the manufacturer's info, if you feel uncomfortable with any of the steps, certainly call an electrician. Good luck!

It looks like the frame would allow you to use lights with 6" spacing. I found a few sources for those.... these have a white wire. They also show both white and green wired ones at WalMart but the green are out of stock. ETA, try searching with this string: christmas lights 35 6" spacing