Not sure about the 22, but
On my 25 I used about 12 feet. I bought 15 feet so I knew that I would have enough, then cut off what I did not need. If you can get the boat so the keel is fully down, tie a line to the keel attach point and feed it to the winch, cut and measure, the go buy the real wire rope. You will need to keep 3 turns on the winch when the keel is fully down. Now- all that said, as long as the wire rope fits on the winch when fully wound up, you are ok since the keel will reach the stop block. A little extra is good. Some run with a slack keel line to minimize the "humm" at higher speed.