Upgrade to GTX 1080 and poor performance?

I've just upgraded to a GTX 1080 from an R9 290X and the graphics performance of this game is now garbage. All other games have received a massive performance boost but R3E is much worse. I understand all the Nvidia settings as I used to own a Nvidia card and have tried many different video settings in game but nothing helps. Can anyone help who has been in a similar situation? I'm beginning to think that because it's relatively old and uses DX9 that my new card hates it.

I have...

Upgrade to GTX 1080 and poor performance?