1- The size to fit the servos is very tight, for slightly larger servos (12 mm thick) I had to grind several edges to make them fit - and this size is very common.
2- For the front servo it seems the only way to get its arm in the center under the swashplate arm is to have the servo stick out to one side with its back - looks ugly and de-centers the COG. What is the idea how to mount this servo?
1. Yes, it is fine for E-sky servos. But for bigger servos, the fiber board need to be sand a bit.
2. The tail have horizontal force and torque. Torque is countered but the horizontal force is not. You need to have the CG on one side to balance it.
4. I have my GY401 below the tail boom mount.