I don't think this is worth it's own thread (because too much downforce) so I'll drop it here.
The Secrets of IndyCar Aero Kits
An interesting write-up on the changes to Indycar rules for 2015, comparing Chevy and Honda's approaches.
It goes over many of the odd protuberences on the differing designs. For instance, the winglet on the front airfoil of the Chevy:
Equal time for Honda:
One thing I've never seen explained is the half-tubular corrugations on the bottom of the airfoil that they both have. Maybe they are for strength. There certainly is a lot of leverage on the attachment point both cross-wise and length-wise.
There is a lot of concern about what happens to all those little pieces when two cars make contact.