The problem is how Blender handles scaling. In order to scale up the armature (i.e. the skeleton) to a usable scale in Unreal, you have to use the “scale” multiplier. Unfortunately this seems to have the unwanted side-effect of not actually SCALING the bones (i.e. changing their dimensions by modifying the position of root and tip), it “scales” the bones (i.e. it tells the FBX format that on top of their known dimensions some scale should be applied).
There’s no way NOT to do this, trying to “apply scale” as you would with a static mesh causes the rig to fall apart.
I guess my question is, if you don’t plan to let Unreal PROPERLY interpret bone scale data, is there something I can do to fake it in PhAT? Can I manually define the distance between bones if Unreal doesn’t know how to read it?