The specs for the Lange Shadow 110 state the cuff material is Lyfran. The Shadow 120 and 130 use PU. The RX line which it is replaces uses the more traditional PU for the cuff. Lyfran is used as the cuff material on all models of the XT3 line. Is Lyfran similar to Grilamid or Pebax? Any thoughts on how it would ski on a fixed cuff boot?