For those who want to step beyond the as provided plans.
In my opinion, the RV-10 cowl set up for a 13 spinner is just not to scale for this airplane. While I clearly understand the benifits of common parts across the Vans models, the standard 13 spinner just looks like an afterthought.
This photo is an RV-10 with a James cowl design for a 14 spinner. The extra inch, I offer, makes all the difference.
Will James no longer sells this cowl, but if enough people pinged him perhaps he will offer it again.