Yes ...just block off the two unwanted ports OR if you want you can re-plumb the 5 port so that it has two common inlets ...two common outlets and one exhaust....this gets you a 3 port with double the flow ( outlet ) of the original 5 port.
Drawing available should you wish to go this strange route.

The main co2 tank valve has a low flow value, therefore any regulator attached to it cannot supply enough flow of gas to feed a decent sized ram....hence the use of a buffer.

Do you need a bigger buffer? See post below.