What is the Largest That I Can Safely Stretch my Ears Without Needing Surgery? (photo)

I think that 4.12mm should be a pretty safe size that will likely look like a slightly large piercing after taking the gauges off for a couple of months. This is also a pretty safe size to have the defect closed without much of a scar (5mm).

The idea behind piercing ears (or any other skin) is that the wound initially created by the piercing heals around the edges with hole in the middle.   Skin holes from piercings do not ever "heal" in the sense that there is smooth skin without any evidence of a scar once you no longer desire the piercing.  Any full thickness skin incision, cut, or piercing will leave a scar.  You will always have a hole there, and the larger you stretch that hole, the more obvious it will be.   My advice - if you think you might someday not want large holes in your earlobes, don't stretch them unless you accept that you may need surgery.