I`ve had a look at those sites and if I was still in Australia I`d be onto it already, but, unfortunately I know live in downtown Tokyo where apartments are the same size as my bedroom in OZ!
"DOWNHILL BUGGY":D I used to work with a guy who was paralized hips down in an rock climbing accident. He built a four wheel, independent suspension, wheelchair with 20"(?) inch wheels and used to do the madest downhills. Had the worst crashes imaginable sometimes but always had the adage of "She`ll be right mate, at least I can`t hurt my legs" ,Crazy man I tell you.
Now, kite buggy, no suspension and rubber balls for tires and steering with the feet=Downhill:eek: , I don`t think my crazy friend would even try that one.