Bandwidth limit settings on the SpeedFusion tunnel should be set for each interface. Because ADSL upload and CEllular upload are not the same.
For the following diagram, ADSL is the highest priority, and Cellular is the second priority for the sub-tunnel. When ADSL is down, We have 40Mbps uploading cellular but it will be limited to 350Kbps.
Guarantee bandwidth setting is more important for a sub-tunnel. It means, If there is congestion, We can guarantee voice call.