I have set up a net where the spokes can use either a ethernet or a serial interface to connect to the network. The spokes will then need two tunnel definitions. The Hub also has two tunnel definitions (same source interface with a secondary address). Tunnels to the hub works great. Dynamic spoke to spoke tunnels are established in both cases but the traffic from the second tunnel (serial) wont use the dynamic tunnel and flows over the hub.
And by the way is there a solution to get dynamic spoke to spoke tunnels between different tunnel interfaces?