I have them running. 20mm per side at the back, 15mm per side at the front.
You have to "massage" the old ones out - with a big hammer (and best an old lug nut on the stud, in case you need it again) and you have to be carefull not to damage your wheel bearings.
Then you simply "pull" the new one in. I made myself a spacer and pulled them in with an old lug nut. Needs about 1 hour for all 4 wheels.
About the safety aspect - you can buy them over here in Germany made by H&R (huge suspension manufacturer) TUV approved. There are no worries about safety if the damn things get a TUV approval.
Greets