I am against using vented caps. Too big a risk, if the tank is full, and maybe you park with the filler a bit "down" that it will leak down the side of the car. Either convert it to mimmick a 69/ earlier vent, (tube high in the filler tube) or plumb an additional fitting into the tank.
That would be my preferred method also, although it is my understanding that these vented caps are not an "open" vent; but use a check valve to avoid fluid leakage just like a rollover valve does. Just trying to give the OP some options here.