Can anyone shed any light on their numbering system please and if they tend to come up small,large or true to size?
I'm interested in the 5007 unwashed.
Waist bands are cut along the grain from a single piece of denim, is designed to allow a little stretch. The same can't be said of the leg of the jean. Even if you could get a clamp in there, you risk busting the outer seam of your jeans before you get any noticeable stretch.
But you're right, the simplest option would be to buy jeans that fit in the first place.