Simulation of double walled CNT in Gromacs with CHARMM force filed

GROMACS version: 2022.3
GROMACS modification: No
Dear Gromacs Developer or Users!
I am looking for the interactions between a double walled CNT and Polymers. For my polymers I have Charmm36 force field parameters. But for double walled CNT i have to develop them. As I followed the available discussion, got to know that x2top is available tool in Gromacs to generate topolgy for CNT with .n2t, .rtp, and .itp files. So, I followed this website “Modeling Carbon Nanotubes with GROMACS - Chembytes” tutorial and model a single walled nanoube and simulate it in water with OPLS FF. Also, I used CHARMM-GUI and modle a single walled nanotube and generate topology with Interface FF,and simulate with water It works well.
But for CHARMM force field and double walled CNT, .n2t file is not available (or support) for CHARMM force field, because when i generate this .n2t file for a single walled CNT, it was saying incorrect format! So, anyone please help me to go ahead. Also, suppose i go with OPLS FF, how to make .n2t file for double walled CNT.

Thanks & Regards.
Anuj Kumar