Don't believe the hype! hahaha.. I really don't notice any difference when I move from 650 to 658 at all. I have played numerous 640 guitars and I really don't think they are any easier. The biggest difference you will feel is in making the nut a little more comfortable, or in bringing the strings in a little. For example, Ramirez guitars make their nuts string spacing at around 43mm or so from E to e'. You can bring this into 42mm or so and you will notice quite a big difference in playability. Both of my 658 guitars are 51mm nuts with a roughly 41mm or so from E to e' and both play VERY well. Scale length is only ONE factor in a well setup guitar. My pinky to thumb is around 9" as well and I have no problems playing even 664 scale guitars, as long as the nut is setup in my range. 1mm from E to e' on the nut makes more difference then 10 mm on the scale makes any day.
650 to 640 is a difference of 5mm from 12th fret to the nut. Very slight change. I can guarantee that you will notice a different nut much more readily. My advice is to try it and you will be a convert! Get a luthier to make you a new nut with proper nut action and height with a slightly narrower spacing and you will notice a HUGE difference in playability. From experience, most Ramirez EStudio guitars SAY they are 52mm nuts. But, mine are both wider at around 53mm with wider string spacing (I have gotten used to them so I like it.. but, if you don't then change it!). I used to have one guitar with a 45mm E to e' and a 54mm nut and I found it very hard to play. I changed the nut and spacing to be 43mm E to e' and it was like a new guitar! It was like my hand could relax all of a sudden!
Try it! You will be a convert! Setup's are more complex than just scale length.[/quote]
I am even thinking about having the string spacing a little wider as there is 1 study that has some intricate picking and fingering around a D chord that is difficult to play cleanly because my ring finger is a sausage. What I was wondering was whether they would make the neck as wide or wider. The Hill Mew World 640 has a 52 mm nut, so again maybe replace the nut. And I thought it would make the stretch in Tarregas study in E minor easier as I injured my wrist.