Iain, as much as I feel players need to be aware of the tackle line, I think making players aware of moving the ball beyond the gain line is key to developing a strong attacking ethic. Awareness of the tackle line is more important when in defence i.e. we want to be tackling them on it and not letting them up to the gain line.

I actually use American football to get players aware of the importance of attacking the gain line, then we move it into playing Rugby but with a similar condition e.g. play has to move beyond the gain line after 2nd phase, if not, the ball is turned over at the next phase. If you always give players the target of moving the ball beyond the gain line, they will think of plays themselves to get it there. Once players consistently get the ball beyond the gain line, then you can look at working on link plays with forwards.