There's a guy called Singapore_959 over at tamiyaclub that has done a great job developing some awesome new parts for the Dyna Storm together with a company called Nimrod Racing. One of these parts is an undertray, and AFAIK they're available for order from
http://www.nimrod-racing.hu/
You can find more information about it in this thread:
http://www.tamiyaclub.com/forum/inde...howtopic=42222