Mainly because there aren't a hole lot of kits, and it's not an easy scratch built project, I've seen a few fly, a little bigger than yours, can't remember the manufacturer, it was a fiberglass and foam design, yes it was this people that used to put out tremendous shows in Iwoa, they still manufacture gasoline. It was a beautiful aiplane, a little on the heavy side, but flew very well, and it was fast, so flaps were very important on this design, so by all means, do implement them and build as light as possible, as its thin ribs are meant for speed and not for floating around. Very worthwhile project, I'd say!