The 501x body is too narrow!
Either use Kamtec for a shell only
Or use ebay for body kit 51338
Example
http://cgi.ebay.co.uk/Tamiya-51338-D...3286.m63.l1177
I have just purchased one and it comes with..
Bodyshell
Spoiler (rear wing)
Stickers
velcro for sides 2xstrips
bodyclips
Instructions
Bargain TBF!
Andy