The moass mod is a mod that was done from the original mojo. it has bigger control surface and a longer fuse. and if im not mistaken they are now all sold as moass anyway. and yes the primo has this stuff already built into it, the primo being more for advance flying and thats not to say the mojo is any less advanced. i have a moass mojo and it was my first gas powered 3d slab and i have not looked back here is a video from my last flight
http://www.youtube.com/watch?v=OJtIu0V8mZk