You could split them, but why? If they were split, I would have to click three different sub-forums to get all the data I want. Do you really need to reduce the number of posts in any given sub-forum?
If you really want to re-arrange the sub-forums, I would delete 3D/Aerobatic/Pattern and delete Fun Fly/Profi and create:
*Pattern/F3A/AA/SPA/IMAC
*Sport Aerobatic/3D/Hot Dog/Fun fly
There will still be inevitable over-lap. Where do TOC discussions go?
IMHO