how to interpolate between different sets of FLAME params?

[ShaYito]

Thanks for your excellent work. I want to ask a question about FLAME params.
If I have two sets of FLAME params (with possibly different shapes, expressions, poses), how can I get an "intermediate" set of params, which can represent a mesh that is in between the original two meshes?
I tried using the arithmetic average of two sets of params as a new set of params to generate a FLAME mesh, but the mesh seems to be broken. Will some regulations help, or this is not correct way to do this?