The money is held by the FCM (Transact) and their clearing firm (Goldman Sachs). Why deal with an IB when you can deal direct with the FCM? What is TradePortal going to do for you that can't be done by going directly with Transact?
I also like to go direct to transact, their commission is more cheaper, but the limit of 273 rt per month, for me, I can't have this volume now