Free fly cam rotation issue

Hey
So I' displaying a unity project on 2 monitors, both set to portrait mode. Trouble is my M1 MacBook only supports 1 external display, so I've had to use DisplayLink to get it working on 2. However, screen rotation isn't supported with DisplayLink, so I've got to somehow shift my Freefly Cam in Unity 90 degrees on the Z axis, so that it's orientated in portrait mode. Sounds like it should be fairly easy and straight forward, but it's not. I have my Cam as a parent of an empty, which has the Z 90 rotation applied to it. And the 90 degree rotation is really messing up the Free fly controls, specifically the rotation which uses the mouse position. The main issue is that when I rotate the freely cam more than about 90/100 degrees on one axis, it starts to curve back on itself and won't complete a full 360 rotation. Whats strange is that I don't have this issue at all when the Cam isn't patented to the 90 degree empty. Any help would be really appreciated. I'm using the Extended Fly Cam script.
Thanks