Length is 6" overall (1" stitched in - you can get away with 3/4") for a strap 1 1/4" (both sides)(but I think you could vary them so that the apron sits in the right place for you). For a strap 1 3/4", I'd add 1/2". Holes (5) are usually 'strap width less 1/4"' (centre of hole to centre of hole), but an interval of 1 1/2" seems rather a lot - what about 1"?