Don't want to cause trouble chaps, but I just dont agree with joining on base in this case.
1. This will involve at least one turn inside the ATZ the opposite direction to the curcuit traffic - basic bad airmanship.
2. What if a wide curcuit was being flown (for whatever reason) You may be positioning yourself from the south for a base join only to find yourself staring at someone head on late downwind in a massive curcuit. Now, I don't agree with 'airliner' curcuits in a PA 28... but just imagine the air accident report - YOU would be in the wrong.
Straight in, overhead or crosswind join for me.
Whats wrong with 'going the long way round' ?
respectfully
Kingy