I'm an experienced 7 string jazz solo performer and I've been experimenting with
scale lengths for the last year or so. My conclusion was that a longer scale was necessary for 7 string, especially with the low string tuned to an A (as is the custom among jazz players). I recently commissioned an instrument with a 27 inch scale to be built for me. In order to get used to the longer scale length I purchased a 7421XL for practice purposes while the other guitar was being built.
The extra scale length has been everything you promised. The articulation and intonation of the low string is dramatically improved and the other strings are finally in balance with the low string.
The problem is that the 7421XL is cosmetically inappropriate and tonally marginal for jazz. And yet jazz is where the 7 string has it's most permanent foothold.
I'm enjoying the instrument. It records well and it's comfortable to play, but the color, finish, and shape of the body and the lack of warmth in the tone make it almost impossible to play out live. The scale length is a wonderful breakthough for a 7 string. If you would build an XL 7string with a more conservative design, I'm sure you could find a great deal of acceptence in the jazz world.
