Okay to use wheels that aren't hub centric?

Some would argue that just using spacers is not safe, so it's all ultimately up to what you feel comfortable with.
If the wheels you are trying to use were made for conical lugs, then that may be enough to keep the wheel
centered on the hub. If not, they i would definitely look for a hubcentric adapter ring, or have one fabricated from aluminum.
Try researching if there is an adapter ring that will match the hub diameter of the z31 (66.1mm) and the inner diameter of your wheels.

That being said, I use 20mm spacers on my wheels, the plastic hubcentric adapter rings the wheels came with and conical
lugs and have never had an issue.

What do you mean when you say they're not hub centric? Do you mean they have a larger center bore so that your hub doesn't center them? Or are they generally not installed as hub centric? If they just have a larger center bore, then that is easy to fix with spacers or centering rings. Otherwise find out how they're normally centered and see if you can do the same on your spacers.

With tapered fit wheel nuts the wheel is located concentrically by the nuts and clamped against the hub when the nuts are tightened to lock it in place and prevent it moving.

So i mean like the center "hole" is larger than the hub thing that protrudes out. Like the wheels kinda sits on the lugs so to say

Not gonna lie, I have almost no clue what you said, and I tried googling half of it too lmao

Some reading info related to this topic: hub centric vs lug centric wheels. http://www.gregsmithequipment.com/Hu…Vs-Lug-Centric

To snugly fit a wheel with bigger center bore onto your car you either get hub rings or hub/wheel-centric spacers (Motorsport Tech offers custom made spacers for this). Alternatively you can also center the wheel via lug centric methods (what 260DET referred to) but it may be more susceptible to vibrations and/or more in-depth balancing.

Basically what I'm saying is that tapered wheel nuts LOCATE the wheel in relation to the hub. But it is the wheel being clamped against the hub when the nuts are tightened that stop the wheel from moving when the car is being driven.

He's saying with the proper lug nuts, the wheel is mounted and centered based off the lugs and lug nuts. AKA lug centric.

Also, if you need to correct the offset on your wheels with spacers, use wheel adapters instead. They can provide much more spacing while retaining the lug centric mount of the wheel.