Thanks all for your advice. I think I'll settle for the 60" as it will see limited use and as my area has a very limited choice of implements of any kind. If an L3200 struggles with a full 60" then I certainly can't go wider and will be mindful not to push it too hard (thanks s219).
I'm getting a new Kioti CK2510hst next week and want a box blade. How wide can I go with it's 24.5 hp? Also any suggestions on brand to get the best bang for my buck?