Are you using the alt+right click command. It tells all the ships you have selected to focus fire on the enemy ship you click on with out actually diverting them from the course you've plotted.

Basically you want to group your ships as they will follow the lead ship's route instead of taking their own route. Then plot a course that crosses the T then alt+right click on the lead ship in the enemies column. That way all your ships will pass in front of the column while focusing their fire on the lead ship.

Word of warning though, if you don't cross far enough in front of the enemy lead ship it might reach your line and then be disabled, thus blocking your ships at the back of your column.