When I 'm playing in the last knock out rounds of CH.L. or Cup, I always checking the formations my oppo using in previous games. So, if he is using the same (or about the same) formation, I would use again 4-5-1 V (which is my favorite formation against stronger teams).
But with def/counters, without offside. The logic says that he 'll start with attack - what else he has to loose- so I would take advantage of my counters.
Another important thing at this stage, is to protect my players with yellow cards, so when I 'm comfort with the first leg, I keep them out of the game.