This is interesting to me too. I've been noodling on the theory and believe it makes perfect sense at the higher engine rpms because the intake flow is quite high and a bad carb balance may require a high flow thru the balance tube. However, down near idle the flows are very low and an imbalance would not need a very big balance tube to correct it, so I would think that the 1" balance tube would have very little value at near idle speeds. Thru the years of doing carb syncs I have noticed that if there is an imbalance it seems to always show up as far worse down in the very low rpms, but as you run the rpm up the imbalance seems to get better. I'm not sure how to explain this except that a small motion of the throttle cable near idle has a much higher percentage change of throttle opening than it does near WOT. Also, the "starting carb" circuit does not become inactive until rpms are higher. What this noodling is leading me to believe is that even if you go with a large balance tube, you should still occasionally do a carb sync at idle. Be interested in other opinions on this.

One more thing, I don't think there is much value in installing a balance tube that has an inside diameter any larger that the smallest hole thru the fittings on each end.