OpenGL / DX11 Interop

We are currently working on redesigning our GUI system in our simulation app.
Our simulation app is using a DX11 based rendering engine (DX11 is required for some advanced features). However, we are highly interested into Qt as a flexible / multi-plaform / poewerfull system for the GUI.

Now the question :
Qt is strongly based on OpenGL, whereas our rendering engine is DX11 based
I know there are OpenGL/DX11 interop options (WGL_NV_DX_interop2 OpenGL extension), at least on some devices (nVidia).
What about the performance impact of this interoperability ?
Our system is working on 3 screens with SLI multi GPU, and we know by experience that achieving optimal SLI is tricky to avoid any paralelisation break down (CPU/GPU denpendency !).
Is this OpenGL/DX11 interop working well with an SLI system ?
I read something about “Implicit synchronization is done between Direct3D and OpenGL”, does this mean we could use this with no bad impact on the multi GPU synchronisation ?

Thanks for your feedback on this subject,
Kind regards,