RE: Copperhead Aviation Venom 45-30
Your discovery is true on all carbs that have the same orientation.
A velocity stack will make a big difference similar to holding your hand between the carb & prop blast. So will installing your cowling to some degree. It may run super rich and your needles may have go in about 1 to 2 full turns. But, if it runs fine like it is why change it? 4 turns out isn't a problem on this carb. Mine are out that far and haven't had a single problem. Like you said, it idles great and the transition is great. So why creat a problem that dosen't exist unless you interrupt the tuned air flow? I was perplexed by this too, at first... but I decided to leave well enough alone and accepted the 4 turns out. I have 192 flights on my V45 and I haven't touched the needles yet.
7400 RPM is a little bit high. I like to keep them around 7000 to 7200. You may want to go to a 22x8.