[Funky Diver]

and two sets of Staff

And you could also share certain forums to prevent duplication? e.g General Discussion could be synonymous on both sides.

In reality speaking, you'd only actually need one board, just by premodifying the user groups through phpMyAdmin.. so adding say 10000 to a members User number and adding say 100 to their user group.

Create a new skin.. assign it to certain groups.

One dB, one board, two different communities.

What would be interesting (and I haven't quite figured out yet... ) is allowing a user to be able to choose their user group on registration (obviously depending on requirements) but an example.

Motorcycle Forum... Themed for Yamaha and Honda riders... but if some one likes / has one of each they can choose to have both options or one of them. Their user group amended accordingly (along with their perms and templates)