17mm is the absolute maximum you can go on the rear without scoring the tire or creasing your fender lip when you hit a bump or pothole.
Design 3 is correct and no additional hardware needed.

 

Appreciate if anyone could point me to the right lug nuts that comes with the motorsport tech spacers - Wheel Adapters, Wheel Spacers, Hub Rings, and much more! | Motorsport Tech
I was given wrong lugs which would not fit on the studs so I procured them locally. But as mentioned on another thread, there's some clicking noise while turning which happens when it gets hot (after some driving). Not sure if it might be the locally procured lug nuts. I've checked, the tyres are not making contact with anything while fully turned.

 

You want the 12x1.5 open end conical.
That is if the spacers are like every other set I have ever known!