Two suggestions better than cutoff wheels for the spool walls. 20'' Pizza Pans, e-bay less than $10 / piece or your local grocery store. OR...Medium or large sized oil drum lids...cost...free? I went with the pizza pans because I did not have two matching drum lids.
I am just now finishing converting my go-cart into a wakeboard winch. I moved the engine to the front, and used the back roll cage as the frame for the spool. I re-used the wheel sprocket, and sandwiched one drilled pizza pan between the sprocket and couplers, then to threaded rods, couplers again, pizza pan and finally another wheel hub. The spool assembly spins on the rear axle that is attached to the rear roll cage.
I actually did not have to destroy any part of the go-cart in the process, so it can be converted back, maybe this winter.