I have seen this before but the idea of doing this kind of sets me on edge. But I cannot really see how to jack the thing up. Some have said a lift adapter that goes under the rear shock mounts or control arm.
Just make sure she does not know that you borrowed the mattress.
I have a black Jack mega heavy duty lift. Last time I used it was a new front tire on the red/black Interstate and it worked perfect with the 1500 adapter. 1800 tires are good for the winter season here but I can give it a go when I get some time off at the end of the month when work lets me out of my cage.