Dan,
Well, the first thing I'll say is if it hurts, don't do it! Reinforcing strain in the hands is asking for problems.
I myself do occasionally use what I call "extension" fingering. That's where I play a whole step between the first and third finger, then pivot up to play a whole step between the third and fourth finger. Even in first position, this can be accomplished without strain if you keep your thumb low behind the neck, and really lean into it so you're coming from below the fingerboard. You MUST pivot between 3 and 4 to avoid overstretching. It has it's uses, and of course in higher positions, it's much easier. Above the 12th fret I use this all the time without having to pivot.
Here's an unusual method of playing a 2 octave F major scale with extended fingerings.
I DO NOT attempt to stretch for these notes in one position, I use the same "dropped" left hand position I use for extension fingerings to reach as far as is comfortable and pivot and shift where needed.
The fingering for the strings are as follows:
E string. 1,2,3,4
A string 1,2,3,4
D string 1,2,3,4,
G string 1,3,4
G ______________________________________7__9__10____________________
D __________________________5__7__8__10_____________________________
A _____________3__5__7__8__________________________________________
E _1__3__5__6______________________________________________________
There are times when being able to do this comes in handy. Slow, exposed tunes in the studio where you need to move without creating fret noise (for us roundwound users!) is one that comes to mind.
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