Mixed elements C3D8P and C3D20P??

Is it possible to use C3D8P and C3D20P elements in the same model? Actually, our model is composed of C3D8P and C3D8 elements, but we need to have a better detail in some regions, so we thought about using C3D20P/C3D20 elements only in those regions.

Does anybody have any experience on this topic? Thank you in advance