Hi,
I found this thread doing a Google search and hope it is ok to revive it.
I'm having the same problem after practising daily for two months.
I can do the spider legs warm-up but once I try to reach for a different string I can't get there.
Here's an example that I think most would be familiar with.
Money (Pink Floyd).
A string second fret (B first finger) to G string fourth fret (B third finger) and quickly to D string fourth fret (F# rolling the third finger).
I have seen bass guitarists use the third finger to pinkie instead of rolling the third. I'm not fast enough yet to do that and I'm sure I could with practice but I feel I should be able to reach a two fret distance even if it is two strings apart. I've seen it done obviously, watching You-Tube tutorials.
I can play some major chords that are only one fret apart. A, C, D. B is a stretch but my index finger is on the high E string so a different sort of stretch.
I hope this all makes sense. My hands are average size I guess. Slender but not tiny.
Guitars are standard length.
I started playing a cornet when I was 10 but took my time getting to the guitar. I'm 71 ;-)
I enjoy practising though and have plenty of free time to do it :D
I'm hoping time is all I need.