John,
I have a Sabre Samurai that I use to trim the sides of trails, but I have not used it on grape vines. I would think the vines are easier to cut than wood. There is a video clip on the Samurai Website that shows a Samurai being used in a vineyard. He has it on a mounting frame that can be adjusted horizontally with a hydraulic cylinder. I suggest you contact the Sabre Samurai for references of their customers who use it in vineyards.