What you want to do is covered in FAA Order 8130.2F. I would recommed you contact your local FAA flight Standard District Office (FSDO). I would suggest you put your aircraft in Reseach and Delevoment, but it sounds like you are just wanting to perform a test for a one time STC.
The local FAA office should be able to walk you through the process. Anyway the order is located on at
www.faa.gov the search for Order 8130.2.
Putting an aircraft in experimental is very easy the local FSDO can perform that task. The problem is trying to get your standard certificate back.
Denny of Oakland