RE: servo installation advice
It looks like the wood is too thin to hold the servo screws firmly. The total thickness of the wood where the servo screws hold onto should be around 1/4", maybe less if the wood is aircraft grade.
You could use 2.5mm - 3mm ply wood to replace the alum. plate to save some weight. Two extra small pieces of ply wood can be glued on top of of it for the servo to sit on it and the mounting screws to screw into.
My concern with alumn plate is to secure the wood pieces to it and the extra weight.