Port end starts have an interesting condition to it. The leeward boat is not entitled to room at the port start mark. Since the red boat is the right-a-way boat she may sail as high as she likes so long that if she luffs she gives the blue windward boat a chance to keep clear. Also, if the red boat established the overlap from clear astern she can only sail no higher than her proper course after the starting bell.

So remember, if you find yourself in the position like the red boat in the above example, you can't go beyond head-to-wind, (for more info see rules 11 and 16) to make the port starting mark. Just another simple rule to remember.