Hi Drmiller, Here is the link to the Vetter Challenge rules :
Vetter Challenge rules
A 3 wheeler is by definition is a motorcycle so yes, please enter. The HyperRocket ( a 3 wheeler ) was the 2010 Carmel Challenge winner. Craig even let a diesel car compete in the 2011 Ohio Challenge. The Vetter Challenge are a lot of fun and have inspired me to participate in " making history".
all the best, Low & Slow