My 24hp Deere uses a BushHog Squealer SQ600, a five foot, light duty model. I've been happy with it. The BushHog vendor had several different models and sizes in their lot. I trailered my tractor to their store and hooked up a couple different sizes and weights before making a decision. I would recommend that to you, if you can.
Otherwise, I agree with Torquin. My tractor is slightly larger than yours, and a 5'er is about as much as it can handle. A 4'er is probably a safe bet.
OkieG