I know there is a slight difference in AFL but if the first tackle has enough shoulder in it , the ball will not go where the tacklee intends.The second tackler should pin the arm ,knock the upper body.The rules are so fluid in the Afl that they ruin the art with their inconsistencies.
When I tackled them at full speed-they never got up ,and I'd get the free too.
The important thing is the impact of the shoulder near the hip.(Keep your head to one side ).