BMUS: I wonder where you operate from. It strikes me that to send you on a route which is very close to CAS as a QXC is perhaps inviting hassle, unless there is no alternative. Is another route perhaps a better choice?. .. .If not, is the CAS a CTR or is it an airway. If it is the former, you should not be scared of calling the ATC unit (in fact, airmanship would suggest it is a GOOD idea) and telling them who you are and where you are going. The chances are then that they will keep an eye on you and will warn you before you get yourself in trouble. We are generally a friendly bunch, you know, and I for one would rather be talking to someone who is skirting along the edge of my airspace rather than for him to be an unidentified blip who might infringe at any time.