Has anybody tried adding flaps to a mono-wing modified AA?

I recently took the lower wings off of my curent AA and I like the way it flies, but I also let the little neighborhood kids fly it in the street sometimes and I don't think they can handle it now because it is faster and climbs too much for them and the limited space we have in the street. I am afraid they will put the thing high in a tree or on a roof. And they really love the thing, so I hate to deny them a chance to fly it.

I would like to add something removable that will keep it from climbing at low power and hopefully slow it down a bit as well. I thought about adding weight to keep it lower, but that will probably speed it up. I think it needs air brakes or flaps. Obviously not retractable during flight, but removable between flights would be nice.

I am thinking about adding a piece of card stock about 1.5 inches wide on the trailingg edge between the props and drooping down to the boom as a sort of flap/brake device. I think this will help, but it is too windy to test now. Maybe somebody has figured this out already? Any advice?

Putting the lower wings back on is no longer an easy option because I cut away the sockets in the lower fuselage where they mount. Adding the lower wings on the ends of the upper wings doesn't help either because it climbs way too much and won't turn responsively like that.

I need a configuration that will stay under 10 feet high so we can retrieve it, and hopefully slower so they can turn it before it gets into trouble.