I'm a HUMS engineer, and I've dealt with dozens of AS365'S with retrofit HUMS, there should be no problems whatsoever. What sort of trouble are you having??
I dispute your point regarding safety and maintenance, HUMS is not a fail safe early fault detection system, however, and the CAA will back me up on this, it definately IMPROVES safety and reliability, and on a machine with so many single critical load paths, that is justification enough for its existence my friend.
Remember, the fact that a good HUMS will save you a few beans in terms of maintenance costs by allowing better maintenance planning and spares procurement, not to mention helping your direct operating costs through reduced downtime due to in depth fault investigations, or unnecessary assembly changes when a small component is at fault, is a side issue. The name of the HUMS game is safety, when you are flying out to the ship, or the rigs, the one sound you do not want to hear is "Splash".
E-mail me privately if you want more in depth chat regarding your specific problems, happy to help.
