I have seen alot of people do suitcase deads and not one of them had an increase in waist size..now the side bend is a different story.

Kb is correct and i forgot to mention,that the reps should be low.

KB you've seen pics of Pavel..his obliques are iron plated my brother.

KB ..Have you tried the oblique barbell twist where and end of the barbell is in a corner and you twist from side to side rotating on the balls of your feet.

I could never feel that excercise or quite get it down.