Hate to disagree Digsy , I too ran with no spigot rings for the entire 9 years-plus with conical wheel studs without a hitch but I always had issues with wheel vibration over 100km/h as soon as I got the Aluminium spigots the vibration went and the front steering tightened up , more direct steering and faster direction change
If you need hub rings , like with most aftermarket wheels the Bore of the barrel does not match the OEM bore , get steel/Aluminium ;
From Mr Wilson
never use plastic or similar , plastic ones are NOT suitable. the wheel studs should work *ONLY* in tension and see no vertical shock loads at all. They will *NOT* centre the rim properly without them if the hole in the rim is bigger than the snout on the hub.
All shock loads should be taken through the hub's "snout", via the well fitting hole in the centre of the wheel.