Chalky, I can only go off my past experiences and you have to bear in mind I am by know means a technical angler, but I've found my hook holds when using d-rigs with fairly stiff, short links for pop-ups have given me far better hook holds that a standard hair rig. I suspect it's to do with the angle that the hook hangs below the bait, more claw like I suppose. Maybe aome of the other resident rig geniuses that peruse the forum can give a better insight? All I can say is I have complete confidence in presenting pop-ups this way although I'm sure there are many variations on the rig that will work equally as well.