I don't know. Let's see what we can find.
Starting with the RFC for DHCPv6:
Section 3, http://www.ietf.org/rfc/rfc3315.txt
IPv6 Stateless Address Autoconfiguration  specifies procedures by
which a node may autoconfigure addresses based on router
advertisements , and the use of a valid lifetime to support
renumbering of addresses on the Internet. In addition, the protocol
interaction by which a node begins stateless or stateful
autoconfiguration is specified. DHCP is one vehicle to perform
stateful autoconfiguration. Compatibility with stateless address
autoconfiguration is a design requirement of DHCP.
IPv6 Neighbor Discovery  is the node discovery protocol in IPv6
which replaces and enhances functions of ARP . To understand
IPv6 and stateless address autoconfiguration, it is strongly
recommended that implementors understand IPv6 Neighbor Discovery.
Right... So my theory is correct by RFC standards. A host should configure itself according to how the RAs tell it to configure itself.http://www.ietf.org/rfc/rfc2461.txt
Router Advertisements (and per-prefix flags) allow routers to inform
hosts how to perform Address Autoconfiguration. For example, routers
can specify whether hosts should use stateful (DHCPv6) and/or
autonomous (stateless) address configuration. The exact semantics
and usage of the address configuration-related information is
specified in [ADDRCONF].
M 1-bit "Managed address configuration" flag. When
set, hosts use the administered (stateful) protocol
for address autoconfiguration in addition to any
addresses autoconfigured using stateless address
autoconfiguration. The use of this flag is
described in [ADDRCONF].
Cool! I love it when I guess correctly!
So, back to the problem at hand... I don't see anything in the dhcpv6s.conf man page that says you can set the M flag in RAs (or make it send RAs period). I think you need a real router capable of doing that function. I'll poke around bit more and see what I can see.