on mac, type this onto your terminal, then relaunch MM:
defaults write com.garagecube.MadMapper logFPS 1
set it back to 0 to remove fps
on windows type in command prompt:
REG ADD HKCU\SOFTWARE\Garagecube\MadMapper /f /v logFPS /t REG_SZ /d 1
at any time you can reset mm to factory defaults, in the file menu