This is a guess, but Glod, are you typing with your palms resting on the wrist rest/pads?
I've been using my fullhand exclusive for almost the last year (also own a classic, but it's hardly used), and I'm inclined to agree with Glod that the fullhand is a bit of a flawed design in term of resting your wrists; but this is only if you type while your wrists are on the rest/pads, which is not the ergonomically correct thing to do.
Your hands are supposed to hover over the keys, palms/wrists not touching anything while you're typing. The likely reason why SA would be more of a stretch would be due to just that - resting your palms on the rests (built in or external) while your fingers are hammering the keys, as the height of the built-in rests aren't meant to be used like that. The profile shouldn't affect reach-ability.
In a way the classic is better as it doesn't give you the option to rest your palms while typing, or the option to get even taller wrist rests so you can do just that (still not a good thing to do.)
Hovering is most easily achieved with a chair with arm rests at the right height, so the palm rests are used only when you're not typing. I've been typing with that particular bad habit for years before it developed into daily aches in the area of my palms, and I'd since corrected that by adjusting my chair instead.