My guess would be that if anything, the gas port might need to be enlarged a little bit.
Reduce the dwell time (time that the bullet is in the barrel after passing the gas port and before it exits the barrel) so the system has less time to get gas into the piston chamber before the bullet exits the barrel and the system depressurizes and evens out, and the rifle will be under-gassed and won't function so well. Enlarge the gas port in the barrel to allow more gas to get into the system during that reduced dwell time and let the system work.
After having the gas block off of an SL-8 and an MR556, i've seen that the gas ports are relitivly small for this type of operating system, so there's plenty of wiggle room.
That being said, I really wouldn't want to be messing with the vent hole on the gas block and take the chance of screwing with the timing of the system. The nipple and vent are there for a reason.