The law's clear on this one, if you're playing a shot and the ball strikes you on the full, the impact's got to be between wicket and wicket. The bit that always struck me as a bit odd is the last bit...
(b) In assessing point (e) in 1 above, it is to be assumed that the path of the ball before interception would have continued after interception, irrespective of whether the ball might have pitched subsequently or not.
So if you can see the spin on the ball, it hits you full on the toe on the line of leg stump but you can tell it's an offspinner that would have turned past leg stump you just have to give it out anyway.