If they are using the same size thermal pads on the 1070 and their 1080 ti, then they are probably using that same pad thickness on ALL their normal sized 1000 series cards. Manufacturers don't tend to want to make things too complicated when it comes to things like small parts. Keep them the same so they can be used on all cards and no need for multiple parts on hand. I'd be very surprised if your card took a different size being as both the 1070 and 1080 ti Zotac cards use the same pad.
You could probably also just use a good thermal paste like Thermal grizzly Kryonaut.