Even on the preset VR low I am unable to maintain a stable 90 fps for my CV1. I mostly get framedrops in stations and close to planets. These framedrops brake immersion for me. Is it even possible to get a stable 90 fps on a GTX970 OC, i5 3570k (4,4 ghz) and 8 GB RAM?
No.
Do you realise that, your GPU and RAM are under recommended spec for this game in VR? Yeah, I can get a single 970 OC'd to the nines, and I'll be doing pretty well at 1920x1080, most of the time at 60+FPS. ED needs to render about 2x the screen area (before it's mangled/warped to be sent to the headset), and do so consistently at 90FPS. Even two such cards in SLI is pushing your luck for Elite Dangerous in VR (although together they do quite well for 4K).
You could try and start from VR Low and work your way down through all the settings to turn them off or to absolute mininum (remembering some settings only take effect when you restart the game), but I'd suggest you look for a cheap 980ti or other AMD equivalent at least. Also, bear in mind that VR is now a licence for more immersion (i.e. rendering effort). You could hold off until the 1180 (namely a quicker 1080 with HBM2 VRAM), by which time there'll probably be at least one 4K per eye VR headset openly in development for consumer use and such a card with it will be just like your 970 now.
I'm assuming you've got your card in a PCIe3.0x16 slot. Hopefully you can whack in another 8GB RAM in your motherboard, too.