These ARC Power rear braces
Peter_VIE mentioned look pretty interesting. Looks like the type 4 upper and lower carbon fiber braces go for 38k yen each, or about $350 USD each on their website, but I can't figure out how you would purchase them:
https://translate.google.com/transla...torefine.co.jp
Any thoughts on how well these might perform? It looks like the upper brace might be beneficial but the lower brace might not be very effective unless it were tied together like an x brace.