PfcAJ clarified his "half way" comment nicely - half way out, not when the dive is turned, so we are in total agreement.There is a pesky thing called "Rock Bottom" or did you not see what forum you are in?
I also know what forum I am in and believ eit or not I am familiar with the rock bottom concept (independent instructors and divers promoted DIR and DIR concepts before GUE was around). But "rock bottom" is no better than the assumptions and conservatism used to figure it prior to the dive. Consequently, if the conditions change to the extent that the beginning assumptions and conservatism used are no longer valid, rock bottom is not going to cut it. That is one of the reasons why 2 person teams are problematic and three is preferred, it adds an additional margin of reserve gas when a change in initial conditons invalidates the initial assumptions.