Former Doniphan Co farmer myself. And like you, I have mowed a few acres of hay with horse and tractor mower. More with horse. Never heard or seen stubb rock guards or whatever they may be, and I have never seen other than under serrated sections. I have sharpened my own sickle, which I bought new in 74 ever since. It is serretted, and the fine teeth can yet be seen on it.
I believe, you can have all the variations available on a sickle mower, BUT, If the sickle is properly sharp, If the rock guards are in proper alignment with the tops pressed right against the sickle slightly, The pitman rod in good shape and tight, and someone who knows how to run a mower, Than you will have no more trouble, and way less expense than one who runs a English Mower as they wqere first called when they first came out, and of the current name of them which escapes me now.