48 IDA fuel level

[Eljaro]

The Weber tuning manual says that the fuel level inside the main well should be less than 5-6mm below the nozzle bottom edge. It explains how to measure this parameter with the help of a Vernier Caliper and a Flashlight.
On anothe hand there is a procedure with special tools on how to adjust the correct float height, which is 5.5mm for the float (not the central ridge) above the lower carburetor body.
If the float level is adjusted to these 5.5mm the fuel level in the well will be somewhere between 10.5 and 12mm, which is not what it should be according to the Weber Tuning Manual.
I am having problems with slight intermitent hesitations or misses when driving with the engine between 2500 and 4000 rpm at a steady speed. It is subtle but clearly can be felt as if the engine would be slightly breaking and going again.
I have checked my ignition, changed the 6AL box and bought a new distributor pickup, even made a new shielded cable from the AL6 to the distributor, with no success.I even have a ground cable going from the engine direct to the ground terminal on the battery.
Under the timing light the timing fluctuates at those engines speeds slightly, maybe 2 or 3 degrees retarding over the 36º set for maximum. The belt also starts to slack up .
I have tried everything up to now with no success.
I suspect that maybe this has to do with the fuel level and some improper aireation of the mixture. I tried to rise the fuel level to reach those 6mm below the nozzle hole in the well but I started getting gasoline dripping out of the pump jets.
The engine idles great, does not backfire or sneeze, accelerates fantastically and goes generally very well.
Only this hitch with this stop and go feeling when driving a steady speed above the idle circuit speed range.
What should the fuel level really be? Any suggestion as to what is causing this missing at medium engine speed?