The Rickenbacker is 2, 1/8" at the 12th fret. I'm pretty sure it's well inside of 2, 1/2" at the last fret. If that's something you're interested in, Jeff Rath, TB's own Ric5 does 4 to 5 conversions. You might PM him, or post something on the "In Praise of Ric5" thread.