Your formula looks good to me.

Now - you should grab the game from SVN http://www.freedroid.org/download/#c47
Then do your modifications, and create a diff with SVN diff, then upload it on
ReviewBoard (RB) http://www.freedroid.org/developer-area/contribute/#c56

As for your patch, the #define should be drapped, just hardcode -0.03.

It's OK to ask silly questions - I hope you have the answers above. If not, just
ask again.