Does anyone know the requlations for "experimental"
  located inside the aircraft or which FAR to look
  under?  Will any font style work?  I believe it has to
  be three inches tall.
 
  I am in the process of getting my upholstery done and
  will have the word experimental stiched into the
  material on the front of the baggage bulkhead.

Art,

 

3 inches, visible from each entry point.

 

If you take out the upholstery for any reason, the aircraft is not airworthy until "EXPERIMENTAL" is again displayed.  What about if the baggage covers the text?

 

What is wrong with the usual spot, the rollover behind the canopy?  Some have put it on the inside front of the canopy so it can be seen only when the canopy is open (same as on the rollover).