I don't like the idea of limiting the diameter of the tubes. they're meant to stop hydrolock, and if they don't flow enugh they may not function well enough to effectively vent off the excess fuel. As far as lengths, 1) don't infringe on the drain screw hole, and 2) make them about 8 mm above the bowl parting line. Do the drain hose dealio and you'll have about as good a setup as can be done. HTH, steve