Coming back on my original question did any one try either zenith carbs?
In the meantime I got the 24mm version, and it works!
One little issue is the quality, the idle needle bore is offset and the needle is too far open making the mixture too rich at idle. Zenith does not respond tot my claim, even when pictures show the offset clearly. Sending the whole thing back to the US will cost me a fortune. Now I machined the bore and I am getting there.
Acceleration is great and the engine is running like new.
With a better service and quality from zenith of would be a good buy🙁