You can change the speedfusion traffic distribution policy. open a wen browser to your device and login, then change index.cgi to support.cgi in the address bar and go to the page.
Then click on this link:
Which takes you to the PepVPN/SPeedFusion profile page, edit a profile and you’ll see a new line:
You can then choose Overflow:
The help text for overflow says:
Overflow - Use the wan-to-wan link with highest overflow precedence for sending traffic. Overflow to link with lower precedence when the current one is congested, or approaching WAN upload / download bandwidth defined by user.