I bought some bib and brace cycling knicks awhile back, and although they seemed fine in the store, I'm finding myself pulling on the legs at traffic lights to relieve the tightness in the crotch. In other words, they're a fraction too small, and I'm thinking of cutting the bits that go over my shoulder and sewing in a piece of fabric to loosen things up. Has anyone done this, or have any other recommendations? Where should I cut it? What kind of fabric would be best to insert?