3ds Max Animation :: Stretch FK Setup Not Able To Rotate At The Elbow

I'm trying to make a FK arm with the ability to stretch in Max 2012, but as soon as I assign an orient constraint to the elbow, the stretch ability disappears. 

The file consists of two bones, two spline controllers, and an expose transform.  The upper arm bone is orient and position constrained to the shoulder controller spline. The exposed transform reports the distance between the elbow spline controller and the upper arm bone.  The lower arm bone, has a "Float Script" on the X Position transform and it takes the distance reported in the exposed transform to adjust its position relative to the upper arm bone.
 
If I select bone_elbow and assign an orient constraint, the "Float Script" on the position stops working, but the rotation works.
  
(I'm trying to keep the controllers out of the heirarchy of the bones because our game engine will export them and I'm trying to avoid that)