I've done it twice now on an 1800, and love it... I thought there was a list of tires that are confirmed fits for the 1300 on that site, but I couldn't find it. Seems like I remember a thread there where they put a Douglas (available at Wal-Mart) 205 on a 1300 and it fit. That was the only 205 that seemed to fit the 1300, so the widest you could go.
If you do it, post some pics up so we can see!