DCO right now does not support mssfx'ing, therefore, if the MTU is not manually reduced, throughput is heavily penalized (right it is set to 1500 by default).
For the time being, we should simply default to a more meaningful MTU when DCO offload is enabled in the config.
This is a similar in behaviour to other tunneling protocols out there.

This can be revisited later on once mssfix'ing is implemented.