Shockingly, SM continue to use their patent on their 1/5 F-16!
Could you please explain your meaning of this statement. No one have seen the 1/5 f16 fin / rudder setup yet.
I would suggest you check installation again. Also check the plastic hinges. Did you make support for hinges - or is it glued with no support. The complete pin hinge must be glued into wood - only hinge should be gap between rudder post and fin trailing edge.
The 1/5 f16 uses wire hinges like f14 , avanti....
Best regards