If your fretboard arm feels uncomforatble quickly you've got the strap too low....but you might not need to change the length. Try angling the neck by shifing the strap on your shoulder. I play metal and I find this useful because if I'm picking the E string fast to do a song like 'Return to Hanger' or 'Holy Wars' i like the guitar quite low with the neck almost at a right angle to my body, but when I get to the solo i get a better action and sound by angling the neck at about 30/40 degrees. Does that make sense? Its kinda hard to explain.
People who play with guitars round their waist often do have long arms. Its a sad fact the the length of body parts can sometimes separate one musician from another....Look at Vai and Page who go from one end of the fretboard to the next using the 'baseball bat' technique....they got massive hands and fingers. I'm stuck using the classic technique for that kinda thing because my hands are just that bit smaller than I need them.
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