Hello Andreas,
There are simple ways to connect mainsheet blocks to boom to clew of mainsail and affect mast rotation and there are complicated ways. Simple ways usually work best and they are lighter weight and less expensive. It sounds like you have a complex system with everything interactive. Check out the ARC system, web site, with a very lightweight boom, small Al tube, in a batten pocket along the foot of the sail with a long adjustable clew plate along the foot of the sail at the clew. Mast rotation is affected by what hole in the clew plate you connect the mainsheet to the mainsail with. An aft hole produces more mast rotation and a forward hole produces less mast rotation. This is a very simple system and no gooseneck is required at the front end of the boombatten. Goosenecks are old fashion, parts from the past.
Bill