IB API sends volume through "TRADES" tick type - which is not available for FX at IB. Zorro's historical data request for "TRADES" (to obtain volume) generates errors.

TCP/IP tuning is definitely important for minimizing latency in RT trading, but much less so for downloading historical data.

Anyway, if you lift the limitation on Zorro's side, your IB plugin can still request data in 300 ticks.
But other people will be able to use it with more flexibility in their own implementations.