It's easy if you're willing to modify one little line in the source ;)

• Get the mousetweaks source (apt-get source mousetweaks)


• Get its build dependencies (sudo apt-get build-dep mousetweaks and then sudo apt-get install build-essential dpkg-dev fakeroot)



• Inside the file mousetweaks-3.4.1/src/mt-main.c, around line 375 (may differ for you) find this bit:

  
  
  

  
  
  static void
  
  mt_main_do_secondary_click (MtData *mt)
  
  {
  
  mt->ssc_finished = FALSE;
  
  mt_main_generate_button_event (mt, 3, CLICK, CurrentTime);
  
  }
  
  




• Change part in parentheses in the bolded line to (mt, 1, DOUBLE_CLICK, 40)

  
  
  
  
  
  • This modifies the code so that the "simulated secondary click" becomes a "simulated primary double click" instead ;)
  
  



• From within the mousetweaks-3.4.1 directory, run dpkg-source --commit, and name your patch anything (it doesn't matter)



• Then run dpkg-buildpackage -us -uc and wait for a bit...



• You will find the appropriate mousetweaks*.deb file in the parent directory. Install it with sudo dpkg -i, enable the "simulated secondary click option, set the time, and enjoy! (note: the double-click occurs when you release the held button...)




• Please add in the comments if you have any problem modifying/building the package.