Not to rain on your parade or anything, but most robotwars related forums are to widespread as it is at the moment. I would rather have less forums with more people on it then the other way around.
Instead of starting my own forum for my website i opted to link to the best forums for the various topics. Robotwars101.org for ants, FRA forum for britisch heavies and feathers, robowars.org for the Aussies, DRG for Holland, and GRA for Germany.
There are loads more out there, but these are the forums where I know people will 99% likely to get the right answers and find the right people.
No need to apologise, you can start your own forum if you want to, no one is stopping you. But I doubt it wil take off as much as you would like it to.