I use the plastic tubing with water, and it's great, but you have to be fast on the kill switch. I've read that you can put a crossover between the two tubes with a valve and use that to keep it from sucking water into the carb.
I had, but have lost a link to a setup that uses tubing and glass jars with stoppers. basically, you have two jars with stoppers. the two jars are connected by a short inverted-U shaped tube that goes to the bottom of each jar. Then there is a tube that runs from near the top of each jar to a carb. You put in enough water to make it work, but *not* enough to reach up to the upper tubes when all the water gets sucked into one jar. The goal is to make the water levels even. Seems like a good plan to me, but I think there will be a lag... it will take a little time for the water to flow across, so I would think you need to adjust, wait a few seconds, adjust again...
A