I put one in our old trailer when doing the living quarters worked very well.

WH

A few years ago, I helped install a LQ in an Exiss trailer. The owner had obtained a used toilet/ shower combination with a base holding tank from a truck camper, and was prepared to use it for his bathroom installation.

The 4' short wall dictated a small bathroom, and the assembly wouldn't fit the triangular proportions the floor space dictated. I could have rebuilt/reshaped the fiberglass tank, but at some time considerations. Another unwelcomed feature was that it would mean loosing almost a foot in headroom. The advantage of couse, was the self contained unit being installed above the floor, with only a water source and drain being needed.

At the last minute, the owner's wife made the decision to go with a conventional Thetford toilet, and we installed a black water tank under the floor. 

With the right circumstances, the camper style, above the floor installation could be an option to consider, for ease of installation and lack of under frame holding tanks. They are available in many sizes and capacities. For instance, a small toilet only unit, might work well in the DR of a BP trailer.