I once have spoken to IBFX cs, and he said that IBFX recommend that a customer should hold position in 90 seconds before closing it. However, he clearly stated that if a customer decided to close position before 90 seconds, IBFX have nothing against it as it is done not via dealing desk. I ahve done this in live trading by taking 1 pip as the TP and it works just fine. So, scalping is allowed in IBFX. Probably the main risk would be slippage though.