Originally Posted by IFixPlanes
You can do a thrust limitation via FMC, but you can not go above the Thrust programmed by the Ratingplug and written down on the Nameplate.
Without going into the complexities, on some 737-800s you can imput a derated thrust setting from 26k to 24k or 22k, and further reduce that derated thrust using an assumed temperature... thus the term double de-rate. If you have friend that flies the -800 with this feature, grab his FCOM. The determining factor in which derated thrust setting depends on the ATOGW.