Instead of eliminating the warning sound you can make it turn on only when you throttle back allmost completely by doing the following:
Go into your Aircraft .cfg.and find the following section: [gear_warning_system] once there you can change the value at pct_throttle_limit=0.37 to what ever works for you.
In my case I have it at 0.15 and now I can throttle back to allmost idle before the warning sound comes on!
I'm not sure what the real airplane is like but slowing down while descending with out having the warning sound come on was very difficult on the original setting!