DrewPeterson7
Sage of the Order
High A is about as high as I've heard of anyone tuning on 25.5." So, you can probably do it, but there are a LOT of things to consider.
For one, you're going to need much lighter strings. I think D'Addario still makes sets of 7s, so go see if you can order those. This is less for the bass strings (though, tuning them up will put a ton of tension on the neck and make it very hard to bend) as it is for the treble strings, which under that kind of tension you'll be popping 9's like it's going out of style.
Also, you might want to look into special strings. Google Gary Goodman - he's an extended range bassist (ish) who plays something like a 12 or a 14 string, and ended up having strings made up out of a special alloy such that he could make a thinner, less prone to breakage string specifically for tuning to high A. He's an, um, opinionated cat, but he does sell these strings off his website (I believe), once you convince him you're not a potential rival who wants one to analyze and recreate yourself.
Here's the site: http://www.octave4plus.com/
Finally, if you're looking to tune up that far... Have you considered a seven string? A seven would allow you to have six strings tuned like a normal guitar but up to Ab, but still leave you a lower string in Eb to cover the normal range of a guitar as well as those higher notes you're after. Chording is a little different on the low strings (basically, the intervals (and in turn chord shapes) don't carry over exactly - remember that there's a major third between the G and B in standard tuning, so if you try to transpose chord shapes down to that lower string, there's a fourth where a major third normally is, and then a major third above that where you normally find a fourth. As long as you play on the lowest four strings though shapes carry over, and there are other chord forms you can use - I'd be happy to help you if you go this road), but basically it gives you the extended range you're looking for without losing all of the low end.
For one, you're going to need much lighter strings. I think D'Addario still makes sets of 7s, so go see if you can order those. This is less for the bass strings (though, tuning them up will put a ton of tension on the neck and make it very hard to bend) as it is for the treble strings, which under that kind of tension you'll be popping 9's like it's going out of style.
Also, you might want to look into special strings. Google Gary Goodman - he's an extended range bassist (ish) who plays something like a 12 or a 14 string, and ended up having strings made up out of a special alloy such that he could make a thinner, less prone to breakage string specifically for tuning to high A. He's an, um, opinionated cat, but he does sell these strings off his website (I believe), once you convince him you're not a potential rival who wants one to analyze and recreate yourself.
Here's the site: http://www.octave4plus.com/
Finally, if you're looking to tune up that far... Have you considered a seven string? A seven would allow you to have six strings tuned like a normal guitar but up to Ab, but still leave you a lower string in Eb to cover the normal range of a guitar as well as those higher notes you're after. Chording is a little different on the low strings (basically, the intervals (and in turn chord shapes) don't carry over exactly - remember that there's a major third between the G and B in standard tuning, so if you try to transpose chord shapes down to that lower string, there's a fourth where a major third normally is, and then a major third above that where you normally find a fourth. As long as you play on the lowest four strings though shapes carry over, and there are other chord forms you can use - I'd be happy to help you if you go this road), but basically it gives you the extended range you're looking for without losing all of the low end.
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