Hi Chris, our arena is built purely for featherweight full combat, although we do run heavyweights for demonstrations (we can run spinners).
The limiting factor for our arena is size, our wall height is not to the FRAs guildlines for heavyweights but lower to the feather class, and our exlcusion zone is 900mm rather than atleast 1m that the Heavyweights need. even if these were increased, the physical floor space wouldnt be enough for a proper fight.