When you increase forces and moments they mainly result in heavier rods, brackets gimbal rings and similar. Increasing torsion moment may require thicker bellows element increasing the spring rates. Any increased force and moment on brackets can be problematic. Typically brackets are attached to thin pipe ends. Forces and moments result in deformation and very high local stresses. Solutions are to make thicker pipe ends, longer brackets, reinforcing pads or rings... All add mass, cost money and cause all kind of problems including high thermal stresses during start up and shut down, sometimes even during operation.
If your design has some NB200 bellows in normal process line the problems are minimal but if you have high temperature or pressure or diameter or combination of these then there is a problem. To get correct solution requires close co-operation between the stress engineer and bellows designer. And both have to be competent on their field. Plants are full of failed and wrongly designed bellows. It is surprising how many of them actually don't blow up or damage other equipment.
I could give more detailed explanation of the decision making and design process but this is a bit wrong forum and the space is limited. Last detailed presentation I made on this topic contains one bellows design over 60 pages and other documentation a bit more.
_________________________
Regards,
Jouko
jouko@jat.co.za