I have been racing the 501x WCE for roughly a year on and off in the US. I race on an indoor low/medium bite, tight clay track. I am simply faster with this car than any other car I own. I have 4 4wd cars (bj4 we, xx4 we, xxx4 g+, 501) and this car has more corner speed, jumps lower and is more durable than any of them.
My only issue is that while the part virtually NEVER break they do take a tweak or bend. The major offenses have been the stock inner 48.5 mm and 46mm inner hinge pins--they often get slightly bent. My solution has been h11 tool steel in 3mm diameter cut to length and polished with a dremel. Also--I was always bending the "standard" non hard ball studs. I replaced them with the Tamiya hex-head "hard" ball studs in 5 x 5mm and 5 x 8mm. These are far stronger and simply do not bend or break.
Add Lunsford turnbuckles and the car has simply been bullet proof.
On another note it looks like the 511 parts are starting to be listed on teh Tamiya USA site which is where I get virtually all of my spares. The new arms look like they give a bit more flex than even the softer Db-01 arms. Also the new body and wing is listed. Can't wait for all the usable parts to come in.
http://www.tamiyausa.com/product/ite...oduct-id=54142