I rode bareback horses, for about a dozen years from the early eighties to the mid nineties. At 5 foot 200+ lbs I gotta say you are probably a bit big for roughstock. Not too terribly many bareback riders that tall, I was one of the taller ones in my association and I am 5'8", so hardly a giant. Same is mostly true for bull riding. Strength plays a big part of it, but your center of gravity and leverage play a bigger part.
That being said there are 6 footers out there in all 3 roughstock disciplines, and in my experience most of those were saddle bronc riders, and they tended to be more on the leggy, lanky side.
Whatever you decide I applaud your decision to go to Sankey's school, smart move, you will learn a lot from Lyle and his staff. I know I did, and I had been riding bucking horses for years before I attended, if you do decide to go with bareback horses, Marvin and Mark Garrett as well as Lance Crump both put on excellent bareback schools