If sitting deep and getting into shape worked at League 2 level surely we would have seen some benefits by now. It just gifts possession to the opposition in danger areas.
Even in the 1 game we have managed to win this season Tranmere had a steady stream of unchallenged crosses in the first half from their right hand side. It was only because they were so shite they didnt make anything of them. You can play for or five centre backs – if you allow streams of unchallenged crosses into the area you are going to concede chances.