wheel spacers

I've been running spacers on the back of my truck for the last year or so. I had them custom made out of Alcoa 6061-T6 aluminum and they are both hub and wheel centric. They also have high quality 1/2" studs. I paid about $300 for them, IIRC. I have had absolutely no problems with them, even hauling dirt bikes, off-roading, etc. Mine are only an inch thick, but I don't think that makes much difference in strength.