I think they are safe. Mine have been on for 5000 miles. May wanna use some blue locktite on the bolts.
I ran them on the second setting for a while, but after scraping my extended bags a couple times in curves, i went back to the first hole.
Never had any tire clearance issues either way. ('02 Electra Glide standard with 140 tire on 16" rear wheel)
A buddy of mine has the same brackets on a '08 CVO Ultra & he had a problem with his rear seat mounting bolt being too long & touching the rear tire.
I checked mine & with the shocks off, the swingarm will actually bottom out before the tire hits the fender.
I also have my tail light wires ran outside the stock fender, so that gives some extra clearance. (Has extended overlay style fender)
Arlen Ness & Burly makes some that are quite a bit more $.