I don't have electric
> trim so I guess I will need an electric trim system as well.  I am
> looking for an installer that is well versed at working with
> composites.  Thanks.

Steve,

When/if you change the vertical trim from manual to electric, you may
also need to re-fly the first 25(40) hours off again. I believe that
this would be considered a major change in the airplane.

Steve, Lorn,

 

An auto pilot with altitude control does not need electric trim.  However, there must be a way to trim the elevator whether it be electric, tab or spring. 

 

An auto pilot does not affect the flight characteristics or have a great effect on the weight and balance, ergo I don't think it is a major change.  If you make a major change and your experimental airplane was certificated under the old rules, before 2001 (?), you have to notify the FAA before you test fly the airplane.  If certificated afterward, you would log the change, fly solo for 5 hours and record the results at various CG's, etc.  So, you must consult YOUR certification as to what is required to satisfy its' requirements for major changes.

 

Another thing you can do is write the FAA, noting what you are going to do and claiming it is a minor change - then ask them to confirm that in writing.  They did that for many of my "minor" changes.