[Dad1279]

You can also do it with 2 valves. Use one for direction, the other to open/close the exhaust from the 'direction' valve. We used this with our 'tetra' arm, worked well.

Here is an example of how to plumb it: http://www.chiefdelphi.com/forums/sh...01&postcount=5

And a whitepaper: http://www.chiefdelphi.com/media/papers/1476