Here you go Experts. Picture if you will, three VPN devices. VPN1 is an ASA 5100 with 7.1. VPN 2 is a PIX 506E with 6.3.5. VPN3 is a PIX 501 with 6.3.5.
VPN 1 is already a hub to IPSEC client spokes for purposes of monitoring and pushing software to all private hosts behind the client spokes. All of the other, existing spokes are PIX 501 6.3.5.
The challenge is to add VPN2 to the exsting Hub and Spoke while also adding VPN3 as a "spoke" to VPN2. Ideally VPN3 would also be able to talk to VPN1 but traffic between VPN2 and VPN3 cannot go through VPN1 due to bandwidth limitations and the traffic that is expected to be generated between VPN2 and VPN3.