I have my 3d arf biplane (Accel hobby) setup free castor. It’s nuts because short coupling. Crosswinds make me want to change it or at least put limits on the swivel.

I like my above post because it doesn’t include the rudder at a weak point (like cutting a notch!) Most of my setups are that of the original I think post here using fuel line to flex but that still stresses the rudder at that spot. I’m too excited to see this use a control horn. Never saw that in any directions for any plane.