Answer for backspin-service

Thanks Dan and Tom
I appreciate that stroke technique can vary from person to person which is one of the reasons why I find your videos so interesting.
I have been practising the backhand serve regularly  and it looks to be working as the ball returns to me (on the floor) from a distance of 9 feet.  One thing I am trying to do is to increase the pure backspin and decrease sidespin so the ball returns back in a straight line and does not deviate to the side. I found your exercise of throwing the ball up and catching it very useful as it allows me to check to see where my bat contacts the ball and the angle and direction of follow through.
I discovered that when standing at right angles to the table ready to serve if I moved my right foot back about 6 inches my left shoulder and body moved to the right towards the table. After the toss the bat contacted the ball around the middle of the stomach. The follow through using the wrist was short but did not come in towards the body as much (which I think was the cause of the sidespin). Using this slight adjustment in stance the sidespin was minimal and the ball took a much sraighter road back with increased speed.
The rotation of the body ensured that I was back in the ready position for the next shot. I realise this is a slight adaptation but would ask be interested in hearing your opinion. Also what angle is legal when the ball is tossed?  When I played regularly the angle was 45 degrees.
Alex