Dura Ace 9100 chainring on Ultegra 8000 crank?
The shaped ‘arms’ of Dura Ace 9000 and Ultegra 8000 series cranks that continue from the crank body into the chainrings have different profiles, so the ring from one is not going to match either the crank body of the other. 

If you don’t care about the asthetics it’s not a problem.