aggregate multiple links to improve throughput. Use ECMP?

[duckwood98]

I am trying to set up a demo for a customer.  Two FWF60Ds.  I have a vpn between wan1 and wan1.  Another vpn between wan2 and wan2.  And dmz straight to dmz.  This will simulate dual isp connections on each end and a dedicated point-2-point circuit in between.

I am trying to get ecmp spill over to work.  What we are trying to accomplish is to use the dedicated circuit until it is maxed out then start sending traffic over the vpns.  We have two large SAN units and this would really help in our replication every night.

Is there a better way than ecmp?