I don't have direct experience with the F-512, but I can offer a similar comparison for the F-412. My Oxnard-made F-412 (aka F-512 Maple) sounds very close to my Corona-made F-412, but it is built lighter, has a slimmer neck (only 1 truss rod), and overall is more resonant and responsive. Nothing wrong with the older F-412, but the newer one was a step or two above in terms of sound and, especially, playability.
I'd say that's pretty accurate. Of my jumbos, I prefer the slimmer neck profile of my NH F512, and it's definitely better sounding than earlier F512s I've played, with the possible exception of
@chazmo's excellent Tacoma build. Mine is definitely better than any of the Corona or earlier examples I've tried, but none of them were anywhere near bad, and still better than the competition.
The '91 JF65-12 I acquired recently from
@GF60 is rapidly worming its way into my heart though. That archback maple projection is just phenomenal, and this one and a similar '96 that I owned for a while are the loudest acoustic guitars I've ever heard. I still prefer the slimmer neck profile of the single truss rod F512, but the fatter neck isn't that much more.If I pare down the collection, I might have to find a nice NH F412, and if it's suitable, sell these two.
The other observation is that I think the single truss rod necks are more stable. When I first bought my F512 (from a GC in Oklahoma City for a ridiculous price), the action was a little high when I got it. I took it to my luthier for a setup, and was a bit crestfallen when it lost a lot of saddle in the process, and came back to me like this.
What's amazing is that the neck has not moved one iota since that setup, despite being mostly tuned to pitch and played frequently. And it has been over nine years now. Action is still a hair under 3/32" on the bass side.
Along with
@wileypickett, I agree that jumbos are where you want to be with Guild 12 strings, as long as your shoulder allows it.
