Dennis,
Here are some pictures of the roll servo installation in my RV8. I believe it is the same as the RV6. There are no issues with the weight since 1. the servo weighs as much as about 1/3 a gallon of fuel (although it's at a greater moment arm). 2. The pitot tube on the opposite wing provides a counterbalancing moment, 3. the RV6 and 7 usually have a left-biased pilot/passenger roll moment. The servo works great in the RV8 mounted in the right wing, and the access to it is easier than it would be under the floor. Good luck with the install, the AP is a great addition to your RV!
-Alan