The wing spars and center section is completely different on the two models, i suspect you would be pushed for space with an underseat installation on a 7. Standard wing aileron belcrank location on a 7/9 is a good location. I know one builder in our chapter is putting it in the opposite wing, but you'll need to fabricate your own attach brackets so this isnt really an option for most builders and there is a time penalty and certain degree of "experimentation" by travelling off the well beaten path.
Try not to make changes purely for changes sake.
I think the also later designed RV8 uses a centersection mounted AP servo again different center section design and location.
Curious, why do you want to move it from standard RV-7 location? You can ofcourse build it however you want, there is some smart cookies at Vans they have allot of people to satisfy and have to make compromises, but all you need to worry about is satisfying you're self, the inspector who signs it off and any potential future purchasers.
The change in wing spar design is actually the more interesting tale and the reason for the change to AP location. I suspect this was made to make building easier and take further advantage of matched hole technology.
