Yes, on my P21, I've just marked the keel uphaul rope in appropriate places (fully up, fully down, halfway). I do have the wire strop as well, but only use it to take the weight of the keel when it's up. I do have the top end of the strop attached to the mast step, but I don't like to think what would break first if I dropped the keel!
Geoff
Parker 21 / 18 Dawn