Hubcentric only.

I had 7mm flat spacers on the rear that seemed ok as they left enough lip for the wheel to centre on. I had a vibration through the car that started at 117 and by 140 you had to shut off as it made the dash binnacle literally blurred with vibration. 15mm hubcentric fitted and smooth as silk all the way up to whatever you manage. Goes to show even a tiny amount of squintounting has a massive affect. Hubcentric only is the best way. (All speeds attained on private road naturally)

I found spacers to be nothing but a PITA on several cars. Those levels of vibration at those speeds sound f.dangerous, honestly.

What people don't realise is that it's the spigot that centres the wheel _and_supports_the_weight_of_the_car_. All the bolts do is hold the wheel in place against the spigot/hub face. The clamping force they exert is at 90 degrees to the force of the weight of the car, potholes etc! I sometimes read on other forums very blasé advice about getting wheels with the right centre bore diameter, with sometimes the recommendation that as long as the centre bore is at least as large as the hub spigot it'll be fine. Unless it's a snug fit it won't! This isn't quite the same as too little of the spigot protruding which is the problem with flat spacers, but the centre bore of the wheel is often tapered so in effect the same thing can happen if the wheel doesn't fit snug on what does protrude of the spigot.

Sorry, this isn't correct. The centre bore centres the wheel as it is installed. After the wheel bolts are tightened the friction between the mating surface of the wheel and the hub supports the radial load, the bolt tension supports the axial load.

Just for reference for anyone thinking about spacers and hubcentic etc . one of the very few places I found that actually do small size shims with hubcentic spigots was Porscheshop . nearly everyone else its just a shim which over 5mm really is potentially going to cause an issue , many get away with 7mm fronts just a shim but its so close . https://www.porscheshop.co.uk/wheel-spacer-shims-6mm-with-spigot.html

I do not think there is anything wrong with a small hubcentric spacer to correct wheel offset as long as it's a small one I've seen some stupidly thick spacers though that would cause serious issues.

I agree, once torqued up the clamping force keeps the wheel in place in normal use, you're right. But most people will torque the bolts with the car on the ground, so it's essential that the wheel is centred accurately, hence the 'snug" requirement. The point really is that the bolts have clearance in the wheel holes and the bolts alone do not guarantee to centre the wheel. The spigot is essential (IMHO).