John,

 

I know that the Columbia people say the 350 and 400 have very few parts in common.  I know the ES and the Columbia have different airfoils, even beyond the cuff.  Martin Hollman, and another designer, Rick McWilliams were involved with the IV and ES.  McWilliams is listed as the airfoil designer for the root airfoil on the ES and IV.  The ES and IV share the same airfoil, the McWilliams RXM5-217 at the roots, and the NACA 64-212 at the tips.  My understanding is there is a linear transition from one airfoil to the other.  I think the root airfoil is a modified NACA airfoil with a larger radius on the leading edge.

 

The Columbia airfoil is listed as NLF(2)-0215(H) at the root and NLF(2)-0215(D) at the tip.  So it's reasonable to consider the Columbia to be a completely different aircraft in the FAA's eyes.  But the Columbia management wants to be separate in the customer's eyes.

 

Source:

 

 

Interesting, the early Lancair have an airfoil number very similar to the Columbia.  I don't really understand completely the whole airfoil numbering system.  I've read the description, but my brain doesn't really want to absorb the entire airfoil thing.