Thanks CaptBones, last night i changed the value from 0.8 to GWX default of 2.0, and it seems to work great.
On a clear night with calm sea, they can still see me about 1.5km away, but on one of those very dark nights, with rough sea, i can close up to about 800m-1km undetected. Works better than with stock GWX!
So 2.0 seems to be the "magic number"