How much mileage can you get out of an argument that a prior art drawing does not teach or suggest the patent applicant's invention because is not drawn to scale?

Unless the reference explicitly states that "drawings are to scale"--very little.  The MPEP specifically states at Section 2125: "When the reference does not disclose that the drawings are to scale and is silent as to dimensions, arguments based on measurement of the drawing features are of little value."