Outer boundries of GLTF with shape keys (morph targets)

How do you make sure a gltf-model with shape keys / morph targets always have correct boundries? It seems threeJS only can see the maximized version, no matter of the current morphTargetInfluences values.

Everything looks correct and can be adjusted accordingly, but when I create a BBox3 with setFromObject() I get the maximized version, no matter of the current morph-state.

Is there some way to apply the morphs so that outer boundries are correct?

The model is later exported as a new .glb after the morphs are adjusted by the user. The result is used in another scene with aframe-physics. Also here the collision-boundries are wrong and based on the largest version of the model.