Here is a set of standard Si's KB had anodised for me, extremely durable finish and have had zero issues with the cranks at all.
So I called Cannondale today and asked what they thought about refinishing a set of Hollowgram crank arms. Guy placed me on hold, came back on after a little bit and said that the warranty manager recommended against it because of safety reasons and warranty being denied...bla...bla..blac. But then concluded saying that powder coating might be the best option. I found that interesting as I thought that might place the most stress on the adhesive they used to bond the two halves. Wouldn't anodizing be safer?
When you guys did your cranks, I assume you removed the spider right and just sent the two crank arms only to the shop?