I use an infra red laser to check the iron temp. My irons hottest point is about 1" in front of the heel so that is where I check it. As for the temp numbers I posted my results, yours may differ depending on your iron, how you check it, how fast you iron, etc. etc. Just try to be consistent in temp over all.
In my experience all coverings, including fabric, have a set point and like paint the ambient temp as well as humidity might play a roll in the ironing temp. So don't hold fast to a set number just increase it slowly until you find it has set. It is a little bit of a pain but in the long run is worth it not having those wrinkle's continuously. It will get those "in the sun wrinkles" but those should go away after removing from the sun.