What to do? Cram in some LEDs!
Step 1: Open it Up
Step 2: Remove the fret buttons
Step 3: Make new fret buttons
To see how that was done, hop on over to Matt's Instructable on how he made the new pieces here.
Step 4: Drill out holes for the LEDs to go into
Check the height of the LED and you'll know how deep you need to drill. To make sure we didn't go too far we applied some tape to the drill bit. Just drill till you hit the tape and you're golden.
Step 5: Insert the LEDs
A dab of glue and the LEDs stay put.