Plutonium

So after taking a good look around I have seen that it is possible to host a SERVER for custom maps for zombies and multiplayer. You can get your mods working, you can join friends in private matches, but you can't do both? I really would like to be able to be able to do a custom map with a couple friends but without the ability to host a private match it is impossible to do so. Is there a way around this or a fix for this?