RE: Heavy backhand Sidespin Loop away from the table

Hi Guys,
Why I want to Learn It
So one shot I developed in recent years is an EXTREMELY heavy side spin loop away from the table on my forehand.  This actually gives a lot of players difficulty, especially in certain positions.
However, one of the best things about it is the feel and control using this shot has brought me, so when I am out of position or get to the ball late and it’s low, I can spin it up with heavy side/top spin whilst keeping the ball low and position it anywhere on the table.  Not only does it allow me to get back into the rally, but it’s often an outright winner.
My backhand has really improved lately, and I fixed how I rotate around the elbow to give the shot much more stability.  However, there is still a limit in terms of the spin I can generate and it’s usually from a more hit and rub action rather than a full brushing action (like the forehand shot).
So my hope is to develop the same skill on the backhand, to really curve the ball with heavy spin.  I know that Gauzy loves doing this (PS: the Gauzy & Truls Lin Shidong games were probably the best I remember seeing in a long time!  😜)
Doing the Shot
I have tried to practice it with multi-ball, but it’s slow going and a bit mediocre.  I am trying to keep my elbow high, a bit like when you do a banana flick, but I feel unsure about the best place to contact the ball and where to swing the arm. 
Have tried to get a nice slow-motion video of when Gauzy does it, but the angles are usually not great.  
My sense is that it’s helpful to have my right leg forward (I’m right handed), but should I hit the ball near my left shoulder, the middle or right shoulder to be able to really brush the side of the ball?   Also, where is ideal for the backswing to start.
Love to get your thoughts.