[lurkingknight]

chrono value with a .2 doesn't matter as long as it is under 400 fps. The important one is you get the value you want with whatever weight you're shooting. 400 fps with .2 is 1.48J Ideally you want to shoot 1.48J with the weight you actually use. In a perfect world when you get 1.48 with a .2 the math says you will get 325 with a .3, but in your situation, you could have a phenomenon called joule creep where you have too much air in the cylinder compared to the barrel, so a heavier BB might get higher J than a lighter one.

I would check that before making any changes to the system. If you are getting acceptable J out of this setup with your shooting weight, then nothing needs changing.

If you're getting low readings, finding an even shorter ported cylinder might be a challenge, you could just drill a slot closer in if you know what you're doing... or you can find the right cylinder... or you can use a stronger spring. If you're going to change between short and long barrels, maybe it's best not to change anything.