IPv6 DHCP-PD - Is there a way to add a hint?

[nwtimberlake]

It seems that in at least one area, and probably throughout their network in the future, Comcast residential customers will be able to request /60 IPv6 prefixes. Is there currently a way to add a request similar to "ipv6 dhcp client pd hint ::/60"? This is the syntax used on a Cisco router, hopefully it communicates what I am asking for.