Normally the stock vents don't leak, but I never say never. I've never had one leak at the rear and I've taken brakes out and put regular manual units in without plugging it. I wouldn't put a vent in the rear with a governor still in it. BUT If the guys who do it all day, everyday say not to move it, they have a reason and I'm not going to argue with them.
what seems to be the reasoning for not putting the vent in the rear of the case?, for years it was the accepted practice to do just that and now it's appears to be taboo, I have always put the vent in the rear of the case and plugged the front one.
