I did not have a place for a Microwave so I mounted a cheap, medium size MW under my cabinets. I did have to install a cross brace in the cabinet to attach the lid to the underside of the cabinet.
I mounted the lid first, then attached the MW to the lid.

Many MW mfg's are now using Inverters to power the MW's. Much lighter 1/2 the weight but they are not Smaller packages. Guess they need to run out of transformers before they begin to put Inverters in the smaller MW's.
Thread here:
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/23603727.cfmJim