Having trouble working with the new Phat system introduced in 4.18

I’m trying to set up the physics assets constraints on a modified mannequin skeleton. But I seem to be doing something wrong. Even the most basic constraints causes the simulation to explode. I’ve been looking at a stock ue4 mannequin’s physics asset and noticed a couple of things that have me puzzled. The first is that when you create a constraint, two identical constraints appear in the skeleton tree. The same constraint only appears once in the stock mannequin. The second issue is that no matter which way you enter the two bones to be constrained, the parent/child relationship is swapped. For example, constrained a calf to a foot always places the foot as the parent even though it’s a child bone. I’m not sure if that really matters. But I would sure like to know why even setting just a couple of simple constraints causes things to blow up.

FYI: I don’t have collision turned on between bodies. The linear limits are locked and the angular limits are set to limited with 45 degree ranges. Angular damping is set to 20. (UE4 4.21)