I have two Andersen levelers and they work as advertised -- I've never had to use them to their limits, usually only about 1", and never had a problem with them. I also carry some inexpensive plastic wheel chocks to use in conjunction with the Andersens. I have a large level mounted on the front of the trailer which I can see in the rear-view mirror, so once the trailer is backed in to the site, I just put the Andersens under the low-side wheels and back up until the trailer is level. Stop, chock, and unhook.
I still carry a box with a dozen or so pieces of 2x6's and usually end up using them under the stabilizing jacks.
Geoff & Jill
& Sierra, the little white monster
2013 Ford F-150 XTR SC Ecoboost
2015 Jayco Jay Flight 24FBS