Don't forget, you're mounting the controls to the same panel the monitor goes on. You have to account for the fact you lose almost an inch off the front right off the bat because the front end of the panel rests on the front of the machine. You have to account for not only the joystick, but also the wiriing that usually extends off and out from the bottom of the stick. There's not THAT much room under there. Honestly, a 15" screen works just fine on a Tully.
To put it in perspective, I'm using a 13" arcade CRT in the Q*Beret, and you can see how tight that is.
