I do think the beta should be closes, and here's why:
1. Keeping a closed beta keep the excitement for other people who have not gotten in. They still have to wait, and their intent to play the mod upon release only increases.
2. Opening the beta will make it seem like a full release. That's bad. Updates to the mod won't feel like updates, rather patches.
3. An open beta will have a larger effect on the people who play the mod. Often towards the negative. They may play the beta so much, they'll over do it, and then you'll have another Anglo-Zulu War mod situation.
4. Having a closed beta allows for more focused reports about bugs and what not, and an open beta is just going to be swarmed with people who want to play, rather than help the mod.
The beta, in my opinion, needs to remain closed. However, simply invite a few more regiments, at least a couple NA regiments, make a NA server from one of the current "Official_EU" servers that no one uses. With this, you'll now have a new community to test, and give reports on the mod before a full vanilla release. The [Nr1-Leib] I'm sure would be excellent addition to a close beta. We're a larger NA community, so we'll be able to give you more feedback with the updates before the vanilla release.
Hope all is well with the current updates, Willhelm. I personally am enjoying the mod very much, and have asked you some questions, and made suggestions in-game already. I've been under a few names so far, so I doubt you'll remember me all that well.
