how to occupy max bandwidth

[colapig]

softether client ---- VPN server1 ------(cascaded)---VPN server2----local bridge--HQ network with servers.

above is the connection that I just formed.
the internet connection for VPN server1 is 100Mb, and VPN server2 is 30Mb up stream/2Mb down stream
the internet connection of softether client is 6M

a virtual hub created in VPN server1 without NAT and local bridge connection
When softether client connect to VPN server1. it can obtain an IP address from HQ network

I copy files from the server in HQ network, speed is around 34-52KB/second
I would like to ask, for this situation, Can I modify the setting to speed up the download process? Now, It only occupied 13-20% of the bandwidth comparing to the minimal bandwidth of whole path(2Mb down stream).

[thisjun]

There isn't any bandwidth limitation in default configuration.
I guess traffic delay is large.