my point was not so much on the issue of power but of making contact with the target and the point about legs is correct. Let's not forget if you do lean over with a cross it can be a long way back to your centre and be balanced.

Scrap, in terms of the jab try it sitting on a chair. take the legs out of it for the moment. Just make a fist and push it out straight. Now do the same thing but turn your shoulder/chest with it.