I would also suggest Garmin. Their controller is by far the best in terms of the interface to make the aircraft do what you want and their control algorithms are very good. I had a Trutrak (now BK I believe) in an old aeroplane, it was pretty good but Garmin is better and is easier to interface to other equipment if that is required in the future.
Installation in an RV is straight forward as RV specific servo mounts are available. The most challenging aspect is routing the wires through the spar - in a 7 there should be some holes beside the elevator rod for just that purpose.