I just discovered that my inability to reach my isolator appears to be suit-related. I can do it in my trilam suit, but using the exact same technique (mine) I cannot reach the isolator in the other suit. But I'm not going to stop diving doubles, and diving them in that suit; I can reach the two posts, and the isolator is the SECOND step in any failure. By that time, I will have closed a post and alerted my teammates, and if the isolator needs to be closed at that point, my teammate can come over and do it for me. Now, I probably wouldn't go into an overhead with that setup, but I'm happy with the risk/benefit ratio for the open water dives, even the deeper ones, that I currently do.