I'm enjoying the new KineFX rig tools. What's the recommended approach for rest angles as input to the FBIK Solver? For an arm with a control only on the hand I'm getting locking elbows, which for bones I was minimizing using a rest angle on the elbow.

Glen

The solver supports having rest angles / transforms (https://www.sidefx.com/docs/houdini18.5/hom/hou/ik/Joint.html#setRestTransform) but they're not currently exposed in the Full Body IK SOP. Note though that it's roughly equivalent to just adjusting the input pose since the solver is trying to minimize the change in joint angles anyways.

Are you running into a situation where your input pose is already hyper-extended? Offhand, maybe introducing a Rig Pose beforehand to give the bad joint a nudge in the correct rotation might help.