Not recommended. If you plug a port on a standard SBA hydraulic valve, the pump oil has no place to go as you are exhausting or lowering the cylinder. Consequently, it goes over the relief and overheats the system.
Valves with spools for single acting applications may be special ordered from the factory. (EXAMPLE: BA13AG3EA0 #133259)
(The Converta is convertible to single acting by replacing the long plug on the outlet side with the short SAE plug in the box. Directions and parts sheets are included with this valve.)