Have run them two ways. Two way cylinders and one way. Current mower I'm stewarding has one way. Having all kinds of trouble getting them to work right.  Land Pride 15' mower on JD 4430. 

I'm thinking preferred method is two way lift, then in operation, run in float mode. Yes? No? Maybe? 

Problems I'm seeing is first, the cylinder they used is too small for the weight, and raises wing by contracting the cylinder, which is the low power side. Pressure runs high and eventually the seal leaks. Also has to be vented and since the mower sits out, may pickup water from rain or humidity. With both ends piped into hydraulics, all that goes away. As is, I often seen oil shooting out the vent cap. 

Also, if the wing is up, only way to lower it is for weight of the wing to force oil backwards from pressure side back into hydraulics. If both ends pressurized, can either float or use pressure to extend it. Linkage is such  that even when fully extended, wing is allowed to float, up or down about 20 degrees.

Don't see any downside to two way. Don't see any benefit from one way, other than cost savings of extra hydraulic line?

Called a local outfit that makes hoses and services hydraulics and he agreed with me. Single action systems probably made to cheapen them up, saving cost of the extra hoses. He said some even go one way on the main lift cylinder. Creates all manner of problems that goes away with 2nd set of hoses. Air and condensation enters thru the vent, causes rust, which then damages the seals and creates pits where oil can leak. 

So to eliminate all those problems, and no downside other than the cost, having him add the 2nd set of hoses to convert to double action. My dad should have done that on day 1.