Neither know the Cartels nor Union bindings... some bindings which work well for the Flag:
The SO uses NOW Drive for his Carbon Flag, pairs well. However, he had quite some quality issues... two broken ratchets and one broken ladder in ~15d use.
I liked the Burton Diodes a lot with my Flag, I'm a fan of the new strap design. No fancy responce reducing padding, nevertheless very comfy. (Would have gone with them, but found out that I can use my split bindings).
Also look at Salomon Quantum (interesting wide highback design) or Rossi XV (not my favourites cos the highback didn't fit my calves, but may work well for a guy). Haven't tried the Nidecker Carbon (my size was not available) but they were recommended by the demo tent guy for that board.
"Yeah... no, that's not clumsiness, that's just being topographically challenged" ~ Noreaster