spacers that are not hubcentric...like the 5mm. how can you ensure they are centered properly? Is just eyeballing them okay?

 

My e30 had non hubcentric wheels. I would usually tighten the lugs a very little bit, changing to another lug maybe once every 1/8 turn. Took awhile to get it tightened but usually sufficient enough to get most of the vibration out when driving. Not an ideal solution but worked fairly well

 

w/ 5mm spacers, the factory ring still protrudes (by about 5mm) and will center the wheel on the hub. this is why almost no one uses 10mm spacers. it ends up almost flush w/ the factory lip, that is no lip left to center the wheel. on 15mm or larger spacers, they can be hubcentric, w/ the new 56.1mm ring on the spacer. hope that makes sense.