Can't get mobile presence radius right

I’m using my iPhone presence as my only Thing. I’m trying out SmartThings without yet having a hub or any Things like the presence sensor (which, I read here, is apparently flaky?).

I’m loving this. Problem is, I can’t manage to define my home’s location radius tight enough. It only goes as far as about 500ft. When myself and my partner leave our home, we take a route that crosses out and then back in to our radius, before leaving again. This leads to…

8.04am: "Lisa has left Our House."
8.05am: "Lisa has arrived at Our House."
8.07am: "Lisa has left Our House."
8.08am: "Lisa has arrived at Our House."
8.11am: “Lisa has left Our House.”

… It should be simply…
8.04am: “Lisa has left Our House.”
… Until she coms home in the evening.

There’s not much I can do about this, I think. SmartThings say that is the minimum radius possible.
So how does the presence sensor work for you guys? This would presumably allow me to constrain the left/arrived radius for us.