Nickname plays with custom skins all the time and if they didn’t work on our server he’d have *edited*ed at me at me about it by now. We allow custom skins but not custom materials and effects because of the abusive and cheat potential. I don’t see that changing anytime soon.
As for interp you’ll have to talk with Lemm because that’s a server setting but in all honesty if your rates are where they’re supposed to be then YOU shouldn’t get any lag. It’s others that should.
If you’re getting choke then that’s likely the cause of any bullet registration issues you’re having and unless you’ve tried it with Vsync on I’m not going to start monkeying with the server. If you want our help you need to at least try what we tell you.