RE: zdz 40 RV carb
I have that engine, and i must say it is an awesome engine, mine has the original Bing carb and in did the first start of the day is painful, but after that, the 5-5-1 method does work, for the first start, if you use an electric starter it will make a world difference, if you wish to hand flip; it will be more like 30-5-1, when i hand flip, i flip until the carb drip fuel then 5-1, since the airplane is sitting on an angel, the engine does not get folded.
the channel in the carb's block is to allow you to flip the carb 180deg, if there is no pulse holes on both sides of the carb.
WT 201 does work, and many 12.7-13.5mm can work.
I would stay with the same carb and invest electric stater, the white Sullivan starter with 5 cells lipo, will spin it very easy.