Vapor Path Sizing (Pressure Buildup)

[Headay]

So I've tried to find this information but haven't came up with a solid conclusion.

I recently bought a dual purpose tower from MD,
it is 3" but connection to the condenser is 3/8, I noticed i was only able to push about 2000-2500w through without getting vapors out the condenser.
so I will be building a shotgun condenser soon to be able to strip closer to my full 5500w power, but I am a bit worried about pressure buildup through the 3/8 coupling on the top of the tower.

Is there a recommended size you should have based on how much power / vapor that will be pushed through the vapor path?
Before i pull the trigger on the new condenser I'm wondering if i should cut off the 3/8 and size it up for safety / speed.

the shotgun will be 1/2" to a 2" with 4- 1/2" paths, that collects back into a 1/2"

Thanks!