Your wife may not need the extra "help" but we found the fold-away handles to be much more effective:
I'd try calling Winnebago for advice on screwing it to the metal framework. I know with some models, they actually install steel backing plates in certain areas for attaching hardware. They emailed drawings to me for my 2002 35U.
Worst case: You could always thru-bolt the handle with nice-looking acorn nuts on the inside with fender washers, all of which could be painted to match your wall covering.