You need to rotate the chain around and find the tightest spot then adjust it there using the kicklever to load the bottom of the run.
Haynes gives 3/8" for post '71 and 1/2" for early Tridents. The early R3 manual
gives 3/16". I adjust it so the edge of the side plate comes up to the centre of the pins when lifted at its tightest point.
Renold Chain gives total movement for horizontal drives as C/50 for shock drives where C is the distance between shafts in millimeters which is 202mm for a triple. So 4mmm total movement.