Well since we're resurrecting an old thread, in between the original post and now:
a). I made a flexible replacement for NACA5 and called it N2 (No-Nonsense - still available from Witch Hat). It was made to Naim's own specification for an alternative to their cable as described in their manuals of yore.
b). Witch Hat went and made an improved cable called the Phantom which walks all over the NACA5 and is even more flexible.
So naturally I'm going to point you in that direction now. I would still use the minimum 3.5m length on Naim amps as, despite what they say about stability, there's still no output inductor on their amps.