We recently added rudder trim, which we bought from Aerosport products. Great company and amazing products! I wish we would have gotten this a LONG time ago. For cross country trips it makes flying much more comfortable because we no longer have to hold pressure on one of the rudder pedals or worse, let the airplane lean in some cases. Was easy to install as advertised. We already had a trim tab on the rudder that we could bend manually, but it just never seemed to be perfect in flight because of varying altitudes and speeds I guess.
I installed it on the under side of the panel right betwixt the pilots legs seen in the photo below as silver. I will probably paint it black and leave the dial as silver eventually.