My two year old daughter recently started playing Beatles Rock band with me, but she had a lot of trouble reaching the buttons on the neck. The strap wouldn't adjust high enough either, so I decided to get her own controller and modify it for her.
For this Instructable, you will need a Torx driver, a small Phillips head screwdriver, a hacksaw, some epoxy and a few mending plates.
Step 1: Disassembly
Use the Torx driver to remove all of the screws on the back of the neck. Take out the circuit board and the buttons so they are not in the way when you start cutting.
Put the two halves of the neck back together and reconnect them with a few screws. This will hold them together and make sure you get even, matching cuts. I decided to cut from after the screw post at the lower end of the circuit board and before the guitar strap knob. This allowed me to cut out about 3 3/4 inches out of the neck.
Step 2: Cutting
Cut from your marks and clean up the edges of the cuts. You should also sand down the rim of the cut edges.
Step 3: Reattaching
Try to use an epoxy that is good for plastic. Most epoxies will work for metal, but not all are very good on plastic. I bought these corner brackets instead of mending plates because they were narrower and I didn't want to have to cram them into the controller while the epoxy was setting up. This epoxy works very fast and was already hardening when I was applying the last of it. This led to the inside of the controller being a little messy, but no one will ever see it once its screwed back together.