[QUOTE=aixaix;16509884]This was sort of my main question...amount of flex, which could affect performance. But it's likely sixes in my example. Still, there are slight differences in the design and shape of the two calipers, with the shorts having less material in spots compared with the longer arms. Mainly the neck area just north of the shoe mounting flat. But the difference in amount of deformation under loading, if any, could be negligable.

I may try the shorts with the curent 27's and the long reach on 700c wheels this summer sometime. But then my controlled experiment might go out the proverbial window what with more introduced variables., etc.