6LoWPAN UDP header compression also benefits if the port number you use for most of your messages is 0xf0xx (even more so if both ports are 0xf0bx).
http://tools.ietf.org/html/rfc6282#section-4.3.3 It is only a byte (or three bytes) saved, but that is an easy byte to save just by choosing a port number fitting this pattern. Gr??e, Carsten
