I had the Piranha tray in my NM. No problems with it but it made access to the firewall impossible. My brother has just picked up an ex council NX that has the ARB dual tray fitted. Its a FAR better arrangement than the single tray against the firewall type. Heaps of room beside the tray to mount an isolator, extra relays, fuse panel etc, and you can still get at the grommet to run cables. All that and you still can fit a full sized battery.
Having worked on both types this is the ONLY one I would consider.
Pic from google.