Originally Posted by target
Maybe I misunderstood him, but when I inquired, I believe Eser said the larger rudder he makes has the same area as the stock 4m rudder, and so there isn't a reason to change it.
I could be wrong.
Eser rudder fits X1 style smaller fuselages used with 3.5m and 3.8m wings. Using this rudder brings vertical tail area very close to X2 specs.
4m Xplorer fuselage has taller rudder post, you cannot use Eser rudder with it. To improve 4m flying qualities, just go to X2.5 or X3 fuselage, both work better than the original X1 style fuse.