Cabane, our club is BMFA affiliated and 3D flying is not a problem, it is just a case of being sensible, as with everything else. (I don't remember there being anything in the rule book to stop 3D flying either)

If you are hovering over the strip, then it is on the basis that you give way to anyone landing or taking off.

The only time that I'm arware of someone being told not to hover over the strip was when the wind was cross strip so if anything went wrong the wind would blow the plane (a 90 size limbo dancer!!) into the pilots. So he hovered beyond the far side of the strip and all was fine.

As for the point about not flying 3D when no one else is flying, how silly is that? Mid airs are very rare, I have not seen any with a plane doing 3D moves. In fact I don't think I've seen any with a 3D plane. In fact 3D flying can give other flyers more space. IF the 3D plane is being flown down low above the strip, then it leaves a huge amount of space free for other flying.