Just a suggestion…
You might want to consider using LogMeIn Hamachi
for development purposes. It creates a virtual network adapter over SSL. Pretty easy to use too. It will avoid any possibility of blocking by your ISP since the connection is initiated OUTBOUND. And that means you don't even need to deal w/ opening/forwarding ports at all (which is more secure anyway). And it will let you more easily control who does and doesn't have access. Of course, your beta testers will need to use Hamachi too.
Hamachi might not be a bad idea for another reason; your own users might want to use it to support the game if they run into similar problems! IOW, make that part of your testing.