Sorry, some of the under cabinet or 'ceiling' mounts I linked to at Amazon are under 2 pounds in weight. I've installed a number of TV mounts, in my RV and my kid's homes. You could use a clamp to hold the mount as you fasten it, you can also drill and use through bolts, in the case of an under cabinet mount, to facilitate trying to drill or screw up from underneath.
Usually when I'm installing one in the RV, I go up in weight specifications since I'm aware the TV will be subjected to bouncing and vibration forces not encountered in a home mount.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI