Found that on the Asus RT-N16 that stock firmware didn't seem to be working 100% of the time. Most times it would require a reboot of the router every time a new client connected, also with a reboot of a computer the rebooted machine would not acquire an IPV6 address either.
On switching to a variant of Tomato 1.28 USB developed by Toastman I believe, everything seems to be working smoothly and properly. At test-ipv6.com I get 10/10 for both IPV4 & IPV6. I only had to use the /64 I was assigned though not the /56, being somewhat new to this IP concept is this proper or will it hinder anything?