Maybe the specified setting for floats is ok.If changes are in order it will be a cut and try exercise to find the magic spot.I think one of the main things concerning float level would be to try and make both the carbs the same--actually in every way and setting like the metering rods and pump.Have seen lots of problems from multiple carbs setups from dissimilar carbs trying to be paired.
Inspect those floats good for leakage or damage and dented floats are unusable.In your tuning you could at some point make a short run then remove both carb tops to visually check that the actual fuel level is the same in both carbs.Inspect the metering rod diaphragms well as one side is open to vacuum and a leak will be into the manifold around the normal metering and cause a rich mixture.
Metering rod adjustment is important to low and mid range mixture ratio and have an effect on economy and plug sooting at light loads.The main jets set the fuel ratio at full throttle but the metering rods decrease the size of the mains at cruse and high vauum conditions.
With throttle closed the stop screws need to be the stop--don't let the linkage hold one off the stop.
Both carbs need to come off idle together and have the throttle plates operate at the same angle all through the range.
With throttle closed the air flow through the carb throats needs to be very very near the same for smooth idle and off idle performance.
The best way to get this is with one of the gadjets like the uni-syn, a friend playing with english sports cars or motorcycles carbs can loan one.Many of the english cars with multi carbs to balance described using a piece of hose like about 1" heater hose placed to the ear and the other end offered to first one carb throat and then the other to hear the hiss of air around the butterfly and from the intensity decide how to make adjustments of the stop.I never developed my skill at this very well--I loved my unisyn to much.
One reason the idle settings are so sensitive is because the air and fuel normally delivered to give a proper idle by one carb is now cut in half because we have 2, and the fuel adjustment and the throttle plates are not designed to meter at that tight setting.I have seen it be necessary to work with the fit of a butterfly to get the air flow down.
I hope Hot Rod Lincoln can speak to these things--the serious racing mechanic has to develop a bag of tricks to keep a performance engine carburating cleanly all through the ranges.

Bob Taylor