Great Ape said:
If Warmoth states a max of 11'', why would you disregard that, and assume that 12'' is fine? Sounds to me as though you could be asking for trouble...at considerable cost, no?
Good point. Here's my take on the subject:
The thing is, they're a cast rather than machined part, so they're a bit brittle. That is, you really can't bend them. They'd rather break if you do. Because of that, it would be risky to shim them in such a way as to change their radius, and there's no other way to do it.
Warmoth mills the slot for them with a flat bottom, so if you install them normally, you're good to go. With a 12" radius, the fretboard is going to be slightly flatter than a 10", which is what they're designed for, so your D-G strings are going to be ever so slightly higher than if you had a more traditional nut that was accurately cut. Is it enough to notice? I would say in 90% of the cases, no. Most nuts aren't cut that accurately, and we're talking thousandths of an inch here. So, most folks not only wouldn't notice it, they'd think they're enjoying an improvement in string height consistency. Besides, the difference would only be noticeable down at the nut where you play cowboy chords. The farther up the neck you go, the less influence it would have. I would say by the 5th to 7th fret, that difference would cease to exist and you'd be under the influence of your bridge's radius adjustments.
All that said, while a 12" radius is certainly playable, the 10"-16" compound radius is a Good Thing. It gives the best of most worlds. Lower chords are easier to play, and higher notes are easier to bend without interference. You can set your action slightly lower without worrying about fret buzz, given a good setup. The LSR sits in its design parameters, as it should. There really is no downside, and nothing to be gained by using a straight radius.
Graphtech nuts can be set up perfectly, though, so if that's the object of the exercise and a 12" radius is the only acceptable solution, perhaps the Graphtech would be the way to go. At least that way, the thing can be cut right, given a luthier with the appropriate tools/skills.