I made mine from about 20' of plastic tubing from Lowe's mounted with zip ties to a cool yellow aluminum yardstick.
With center of the tubing at the bottom of the stick, the tubing runs up each side to the top of the stick and then to each throttle body.
Tubing is filled with ATF, which is red and looks good with the yellow yardstick(very important).
I hang it above the bike and there's about 7' of tubing to run to each TB.
With the ATF level at the halfway point on the stick, there's time to correct the setting or shut the engine off to prevent the atf from going over the top, if the tb's are too far off.
It's just a big U shape hung on a stick.
Total cost; about 12.00 bucks.
I'm curious, how close are the levels and how much do they fluctuate when the TB's are "balanced"