Hi,
I don't have a KX500 but I was mostly riding mx tracks because of the total lack of (legal) trails altogether. After a move I finally had the chance to try out trails and man, did I love them, blasting over whoops and keeping the speed up, I was riding alone and with lots of quads in that trail system and two way trails was scary. One time I went around a deep spot of water and just as I turn into the trail on my side of it, I got run over by a quad (trx450r)
I was about half way under the quad, good thing I had full body armor, only had some blue spots. That kind of stopped me from going there again and all the drunk people with guns, too scary!
Now I actually have my own private trails and I plan on using them a lot, just a little scared of the bears haha.
All the talking here about the 500 really makes me want one, but I'm not sure I can manhandle one... I'm 145lbs and about 5'6