Switching Boxes...
I don`t know about this whole muscle memory thing, but an old guitar teacher taught me a brilliant lesson, or series of lessons, on moving up and down the neck quickly. I`ll try to tab it out.
Basically, going from the first fret to the twelfth fret, you want to have only two shifts in hand position. I know this doesn`t answer your question exactly, but I think if you practice this way, and work on getting fast with it and doing it with your eyes closed, you will solve your problem.
So, here goes...
shift shift shift shift
0--1--3--4--1--3--4--4---2--1--4--2--1--1--0
g]]--0--2--4--5--7--9--10-12--10-9--7--5--4--2--0
The bottom line is the actual tab on the guitar, which is a g major scale played on just the g string. The line above it are the fingers you play it with, and above that, are where you should shift. Note that the `s` of shift is in the correct position. Also, note that the shifts come at different times and places depending on going up or down.
Play the thing very slowly and evenly, making sure that there is a fluidity between the shifts. The best way to get real fast is to start real slow.
hopefully that works. check the notes, too. Im typing on a german kezboard, and I haven`t seem a guitar for a month, much less played one.
Hope it helps.