Personally, I would not install a bra. First off, the ones I have seen use fasteners anchored into the RV's body. That means one hole for each fastener. There must be at least 20 or so on the ones I have seen. So what is the point then? Now you have a sheet of black vinyl covering the front of your RV, with 20 holes/fasteners holding the bra in place, then you have to deal with the buffeting of the bra against the paint on your RV. If the bra is not perfectly tight, it will flap in the wind, destroying your paint.
Some say wax under the bra and that helps.
I don't think a bra is a good solution.