Take a thick white tube sock, (Yea, the kind you wear on your feet) slide the fuel tank inside the sock. Zip tye the sock around the fuel tank stopper. Trim the excess sock off. The sock will pad the sides of the fuel tank.
Add Dubro foam to the upper and lower sections of the fuel tank compartment so you can adjust the height if need be.
Servos, Use the locations called out on the plans.
A Dubro S-16 drops right in.