I made my son and husband felted slippers from the Fiber Trends pattern. I threw them in the washer and got called away by my sons (2 and 5months). One thing led to another and I didn't think about the slippers until everyone was in bed. My son's are just about perfect. My husbands are a tad small...okay, they fit me...I don't need slippers and I cannot afford another 4 hanks of 220 to make him another pair. If I wet the slippers and stretch them will I do them any harm?
I've tried stretching felted stuff before and didn't have much luck. However, what do you have to lose? They obviously don't fit the intended recipient, and you don't need them, so I say give it a whirl (or rather, a wetting) and stretch away.