Have you met the engineering and records research requirements? Depending on the age of the aircraft, you may find it cost prohibitive to move to MSG-3. I took delivery of a new GIV in late 1999. We began the research in early 2000, with about 200 hrs TT, to move to MSG-3 (which we ultimately did). Even though the aircraft was relatively new the required records research wasn't cheap or quick. But we determined the cost savings of an MSG-3 program (relative to our type of operation) would pay off in the long run, so we made the investment.
YMMV