How can I assign atom classes from amoeba18bio to speficied atoms during parameterization?

[Blossomstripe]

I'm preparing the force field for a covalently modified serine residue using poltype2. My aim is to use parameters from amoeba18bio to describe the serine backbone to ensure compatability, and keep these parameters fixed during parameterization. However, I cannot find the way to control this in README. Is there anything I can do?