Is this a recent occurance? What was the last thing you altered or worked on?

"blipping the throttle" and "restarting" bringing the idle down sounds a lot like a sticky butterfly or over-run valve in the butterfly. If this has been happening from "day one" with this engine combo (or since the carbs were last put on) it could be a mis-aligned butterfly in the shaft or a binding interlink between the carbs (or the afore mentioned overrun valve).

The float difference is not a major concern (although you are describing H-type floats and not HS type floats) as the level of the float is adjusted with the solid type floats by altering gasket thickness under the needle valve. This can be done regardless of the cover type.

I'd also check to ensure you have proper clearance between the fast idle cam and the throttle lever. Also, try separating the carbs by loosening the interlink clamps. If this is mis-adjusted you can get one carb being forced open, even with the throttle closed on the other.

Mike!