CN-301 TYPE I or TYPE II Change Description

I have been looking around Van's website, this forum, and the internet in general, trying to find a description of what is changed by spar modifications allowing the RV-3 and RV-3A wing designs to operate in the aerobatic category.

Van mentions that the are required to be accomplished, and identifies them:

• CN-301 TYPE I (1/8 inch thick spar bar stock with 1/8 inch rivets)
• CN-301 TYPE II (3/16 inch thick bar stock with 3/16 inch rivets)
  

But I haven't been able to figure out what is being changed, and how impactful the change is to a completed set of wings that has not yet been modified.

I am interested because I am shopping for an RV-3 project, and not all of the potential airplanes have received the modification. My preference is to operate in the aerobatic category, so I would like to understand how much work is involved in retrofitting an existing wing with the modification.

Can anybody who has incorporated this change into an airplane please give me a rundown on what the retrofit entails?

Thank you,

Rick