If ure getting wheel adaptors call cary ar CT performance inc. As for them being safe they are stronger the the aluminum ure boting to them, speaking of the rims themselves. As for them being safe..... if u tow heavy and a lot i would steer away from them but if not then i wont lean u either way.
As for failures, most of the time they are with spacers and not adaptors. When spacers are used that dont give u new studs to bolt the rims too and simply space the wheel out on the exsisting studs are the ones that usually fail. They put way too much stress on the studs. Make sure u get hubcentric adaptors also as thats what u need for SD wheels.
As requested.... check out my sig for OBS truck with stock SD 18s on 35s.