I cut the bottom 7 inches or so off of a XS 997.
I didn't sew it, and never had any issues with unraveling or fraying. The material is just such that it isn't an issue. Wore it daily for quite some time, including several trips to the pool, without any further issues with rolling up, or fraying on the bottom.
I actually found it to be FAR more comfortable once the compression on my stomach was gone, in addition to the rolling issue.