RE: 1/2a pylon racing kits?
you might try building a hot dog, layout is on the design contest page. it is loosely based on the old 1/2a hornet design, which was a 1/2a pylon racer from the 70's. hornet plans still availiable. rcm catalog, I think. I sell the hot dog as an arc if you are interested. just pm me for details. it is about 230 sq. in. a little oversize of the minimum, but flies excellent as it is.
the hornet had a few problem areas, mostly a notched spar, short nose (tail heavy if not careful) and 3/32 tail. small tail area on most pylon designs, ok for racing, but if it is a couple mph slower and tracks straighter you can fly a better course and carry more speed! I used to fly a sonic in 25 quickie and regularly kept up with more modern designs as mine was a LOT smoother. I saw a dominator flat spin to the ground once as the tail too small to stop the spin... again, fine for racing but not the best sport flyer. the sonic was a great sport plane, as was the original spickler q500 (I have one of those right now, excellent flier and fast.).
I hope this helps!