On the subject of avoiding casing abrasion from the rails, it occurs to me that one could put a piece of belt leather with slots for the strap between the saddle rails and the tire. Still a bag would be nice for carrying an inflator, a lever for lifting a dead tire off the adhesive if switching to the spare, and a place to put one's phone. I do wonder just how well the Arundel does with good 250g sew-up. I'm not too concerned with stiff tires here as I'm more likely to carry a patched Vittoria CX or Veloflex as a spare.