Thinking of switching to 4-flat towing

We have been towing a Ford Focus since 2012 without issues. We use the Roadmaster Invisibrake you mentioned. I really works slick. There is never anything to do. It just sits under our passenger seat. One downside is if you change your toad often. You would have to take it back to the shop and have it removed and re-installed in your new toad. We are going through that now. We are replacing the Focus with a C-Max. I took the Invisibrake controller itself out of the Focus and will have Roadmaster install it in the C-Max as well as a new baseplate and wiring. I am lucky, I live in Vancouver, WA which is where Roadmaster is located.