Kirkster is building a hard cab for his 5518.
It appears that Curtis as one time built a hard cab as well, with soft doors. However, now these cabs are extremely rare - mythical as described by "Formula" who sold one.
Here are the pics of the hard cab for those who are interested in the history of these 'last forever' lawn/garden tractors.
FYI: Formula is a source for attachments for the 5000 series for those who are looking for attachments.