And a unmodified 512Ke, since this is essentially operating as a Plus. Since you have a Plus, try reducing the RAM to 512K and see if your 6.0.8 server disk will still work. That will settle question.
Either way, I'm pretty sure there are solutions for running TCP on System 6. My point is not to take anything away from you, and I know we all appreciate new solutions to the same problems. I think the real point of my post is to confirm whether you can do it with only 512K RAM, which is what you suggest you are doing by calling it a 512Ke, but not actually doing since it has 1MB RAM. That's all I'm saying.