I decided I should set up a plane to make use of a Flight Controller using more of its capabilities. Things very few people ever do....

In the "Angle Mode" of control - which will be '2D' for a, EagleTree Guardian, or 'SBAL' for a HobbyEagle A3super - you get to set precise aircraft Angles... Attitudes.
To command an Angle you send an RC command signal, just as you always do BUT they are acted on in a different way than a 'plain' Rate Mode form of aircraft control. Basically the -100,0,+100 range is taken as an ANGLE you want.... from -ve, through zero angle, to +ve. eg Full Left Roll Stick means "Bank left (minus) to 45deg", and vice-versa for right, and ZERO degrees at centre stick. Centre stick is taken as a command that you want NO Angle... zero degrees.
The same functions apply to Pitch.
Typically Rudder is not controlled in this mode of control as it is only of use to control angles for Roll and Pitch as they are what can set a plane to fly LEVEL. The units do not know compass directions, and they do not know anything about the wind/airflows, so they "can't" make sure the Rudder heads you in the right direction anyway.

So what uses can we make of these Flight Controllers, apart from the simplistic use of "Both Pitch and Roll Sticks centered means we want 0deg on those two axis, thus it will AUTOMATICALLY LEVEL and aircraft for you" = Self-Level, Sef-Balance, Recovery Mode etc.

I am going to use a Tail Dragger as the test example, because they add an extra dimension of difficulty compared to tricycle gear aircraft.....
Specifically my Avios 1200mm Sea Fury Camo version will be used.

I will add the OpenTX setup details, with Pictures, as I set mine up.....