Problem is that most of the spacers are 6061 T6 extruded aluminum, sometimes called aircraft aluminum or billet.
6061 is quite malleable, much much softer than any aluminum wheels.
aluminum wheels are cast or forged out of a stonger grade.
for these wheels to set right on a CUCv the spacers need to be at least 2 inches thick.
The portion that is held on to the trucks studs with lug nuts is not as much of an issue as the studs that are in the spacer.
yes they will work, but will wear out too quick for me. and for the $100 apiece that I've seen them for, I'd think any shop with a lathe and mill could make some steel ones.
now if the spacers were forged out of 7076 aluminum I'd feel better about them.
again I work with these materials everyday.
(and before you ask, my boss don't like his equipment used for other than his work.)