I had the same thing in my RV6, but I didn't want a trim tab on the rudder.
Finally, I attached a spring from the right rudder pedal to the lower gusset on the firewall. It took a couple of times to get the correct tension on the spring, but in the end I got a perfectly centered ball in cruise flight. I think I got the spring from Home Depot and ended up cutting it shorter to add some tension. There are no problems with interference...basically, it is the same idea as VAN's aileron trim. Of course it only gives right rudder pressure, but I never needed to give left rudder, anyway.
If you decide to try this, don't forget to put a piece of wood between the gusset and skin when drilling the hole for the speing end, or else you might get a hole through the skin, too. I used a #30 drill for this hole.
On the rudder end, I extended the metal strap, that attaches the rudder cable to the pedal, forward a bit. and drilled a hole in that for the spring to attach to.
Worked great...cost was less than $2.00...and no trim tab on the rudder!