It turned out that my issue was with my router - it seems BT HomeHub 3 and 5 have issues with opening individual ports. I had tried several times, double checking every step, but when I clicked 'Confirm' nothing happened.

After checking online I found many people with these routers have this issue (hence me asking what others have), so I tried DMZing it, which forced all the ports open, and it worked.

Edit - this was not quite correct, the issue came when trying to forward the port to my PC, not when trying to open it.

Just had a thought - What type of internet routers are you all using? I'm on a BT HomeHub3 (Type B) and can get around this issue by taking the dangerous option and putting my PC into a DMZ whenever I host a mission.

A friend and I are having the exact same issue here. We haven't been able to connect since the GameSpy system was shut off. As I used to host for our group being the main editor of maps, we are all missing out now.

Thanks for checking, I didn't think of that :)

Well there are already retractable undercarriages on helicopters, and functional doors on the sub, and in ArmA 2, there was a SCUD launcher that had to erect the missile prior to firing. With this positive track record, I don't think it would be particularly difficult to implement, the only issue I could see would be how they move the camera with the physical model. Upvoted.