IPv6 prefixes longer then /64: are they possible in DOCSIS networks?

Hello everybody, It is commonly agreed that /64 is maximal length for LANs because if we use longer prefix we introduce conflict with stateless address autoconfiguration (SLAAC) based on EUI-64 spec. But SLAAC is not used in DOCSIS networks. So there seems to be no objections to use smaller networks per cable interfaces of CMTS. I was not able to find any recommendations anywhere including Cable Labs specs for using prefixes not greater then /64 in DOCSIS networks. Some tech from ISP assumed that DHCPv6 server may generate interface ID part of IPv6 address similarly to EUI-64 so MAC address of the device can easily be obtained from its IPv6 address, but this does not seem like convincing argument. What do you think? Dmitry Cherkasov