Charlie - Attached are a few pics that I hope help. One you will see the Hacker Q80 front mounted. I do plan to add a rear brace to help provide some additional support. There is no internal firewall with this setup. The aileron servos mount from the inside of the wing using hex servo screws fastened with an allen key secured to the end of a long dowel. Since the slot in the wing is just for the servo arm, you have to install the servo arm onto the servo before putting it into the wing (you have to rotate the arm so it fits through the hole). Be sure to turn your brass screw bushings around so the flat spot is on the top of the servo, otherwise they'll dig into the mounting plate. Larry cut the slots in this plane, so I can't really recommend how to determine where to cut, but I can say that you need to figure out which servos you want to use because the height from mounting tab to servo arm differs between servos. I was hoping to use my DS9411s in there, but the control arm wouldn't line up with the slot since they are not as high as a DS8411. In addition, I would have had to add a spacer in the mounting plate since the servo mounting tabs are not as wide. Hope this helps.
Steve