I see there is some confusion over the position of the knife in the DIR configuration. The knife goes on the waist belt to the left of the crotch trap, basically in the center. In this position it is most accessible by both hands. In this position is does not punch into the legs or suit when gearing up , climbing a boat ladder, or bending over. In this position , it has the least chance of being lost or hanging up. 

When diving open water with no canister light, the long hose goes under the knife in this location. 

When squirreling through small stuff in a cave or wreck, the knife is momentarily slid to the left so that it does not catch on anything. If the stuff is really small and there is no stage, the pressure gauge can be parked under the knife to the left to hold it up as well. This is accomplished at the time  small stuff is encountered, and then the knife is moved back into position when clear of the restricted area. This usually implies no stages, so both hands can still reach it fast, , but still can get it more slowly if that is not the case. This implies not being in a moving situation where fast knife is necessary, but in a situation where just being able to get it will suffice.. With open water diving, by definition, there is no crawling through small stuff, and hence no issue with putting the hose under the knife. 

I really wish everyone would stop trying to second guess all of this stuff , pay attention to the details, and take a leap of faith that the system works for all types of diving.