Step 1: Opening Up the Controller
Step 2: The Spots to Use
My favorite spot to use is right behind the left stick in the top portion of the controller. you can use that spot for 8pin dips like a picaxe08m or a 555 timer, and there is a nearly identical spot on the other side. Heres a link to a picture i made explaining the method http://www.picaxeforum.co.uk/attachment.php?attachmentid=7580&d=1300511581
For a project that I'm currently working on i need to fit a picaxe 18m2 in the controller, but i didn't want to remove the motors. I'm using a wired controller, because its a much more simple board and its easier to modify. I was able to cut off a whole section of the board and remove a few screw posts from the shell of the controller without loosing any functions in the controller. I used the hole where the screw was to fit the programming jack for the picaxe. the result was enough room to fit not one, but two picaxe 18m2s in the controller. Heres a link to a picture i made explaining the method http://www.picaxeforum.co.uk/attachment.php?attachmentid=7581&d=1300511603
Another interesting way to put mods in the controller is to make a pcb that is designed to fit around all of the button holes and such to increase the area of usable pcb space.
Just pick one of these three methods and you wont have to remove your motors. Enjoy