Vtails have been considered custom configurations pretty much as far as programming goes. With the introduction of autotune the process of finding the best PIDs was made much simpler. The remaining obstacle was finding the best motor layout and mixer settings. Having built 3 different sizes from 285 to 500mm I have found one setup seems to work well. The response is symmetrical and autotune will complete with valid values. To make it easier for others to get their vtails in the air quickly below are the motor layout and mixer settings. In order to enter the custom values into the TL mixer you must choose custom vehicle type. Perhaps devs will make it a new vehicle type in future. Motor numbering follows standard TL quad convention. (Note it is very important for a vtail to have rigid tail construction in order for autotune to complete)
The only adjustment to the mixer that might be necessary is if on takeoff there is forward/backward tilt due to COG or smaller props on tail motors. If it tilts forward reduce throttle curve1 motor pairs 3&4 10-20 clicks. If it tilts backward reduce throttle curve1 motor pairs 1&2 10-20 clicks.