Dan,
I have gone back to try testing your opencpn v4.2.1 filter version downloaded from the google drive. I cannot see to find the "IIR Filter" setting in opencpn.ini to change it from 9 to 0 for testing. What am I doing wrong?
-do I have to add it manually?
-if so, where, which section?
ConfigVersionString=Version 4.2.1 Build 2016-03-09 <-- Thought this was the right one

Sorry Dan cannot see the script.