I struggled with this same issue. I have a commercial license. Can't use the KF for anything in that regard so didn't get the medical. The plane is designed for low and slow so flying in excess of 10000ft is rarely necessary for most of us and I can go to 12000 to clear terrain. I don't enjoy flying at night any longer and Im endorsed to fly into class B so that leaves retractable gear and constant speed props as issues for a Sport Pilot. Obviously the gear isn't an issue with a KF (maybe amphibs) and the prop choice is then limited. Weight is what I found as the issue. If need be, anybody who purchases my KF can change the Wt limit and they can put on a prop of their liking. For me, the in flight adjustable prop is what I have sacrificed by flying as a Sport Pilot. Weight is a little bit problematic but not so much 95% of the time. Looking for a 5,6, or 7 may limit you as some are registered at the 1550 wt limit. Build your own and you will just have to respect the sport pilot limitations as I did. Im flying the hell out of this plane and I really don't have any complaints. Some day, hopefully, the weight for the sport pilot may increase. Hopefully a self adjusting
prop gets accepted by the FAA. I will be one of the first to purchase that prop. I doubt your ADD is going to stop you from getting your medical for the PPL but if your like me, you won't often be restricted to the Sport pilot limitations too often when you consider the purpose that the KF serves most of the time. Low, Slow, daylight flying. Best of luck to you.