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I have the regular fret rocker with the four sides measuring 4", 3", 2" and ~1.25". I believe that they were designed with an acoustic guitar in mind because around the 17th or 18th fret there is a cross-over with the 2" side being too long and the 1.25" side just barely bridging the 3 frets. IMO for electric guitar the 2" side should be a little bit shorter. I looked around for such an animal but found none. 
Dremel to the rescue! I used grinding wheels to put a notch in the corner between the 2" and 3" sides, which now measure 17/8" and 2 13/16" inches long. It doesn't sound like much but it allows me to use the ~2" side comfortably all of the way up to the 19th fret, leaving only the 2 higher frets* for the 1.25" side. So instead of grumbling and cussing I now check the upper frets with a smile on my face!
Steve Ahola
* All measurements made with a Gibson neck.
Dremel to the rescue! I used grinding wheels to put a notch in the corner between the 2" and 3" sides, which now measure 17/8" and 2 13/16" inches long. It doesn't sound like much but it allows me to use the ~2" side comfortably all of the way up to the 19th fret, leaving only the 2 higher frets* for the 1.25" side. So instead of grumbling and cussing I now check the upper frets with a smile on my face!
Steve Ahola
* All measurements made with a Gibson neck.