After many times ending in troubles with the standard solutions, I ended up using a fuel pump and the life got lot better. Indeed it is not the cheapest way but that is how those pro-guys are flying all the time while all the others are ... fixing tubing most of the time.

Note: some OS Carbs(needle) were 'famous' of generating bubles(small !) inside; there were pretty many posts in the past, especially for OS 52; it is worth checking in RCU search. How big are the air bubbles is indicative - if they are tiny small ones, then the tank is not the problem, the needle is.

Cheers,
Nick