Hm... I'm getting multiple different things that work. For instance, this works, as well as inverting the "less than or equal" value.
<img src="http://imageshack.us/a/img690/6484/workszm.png" border="0" />
I think what may be happening is that it always calculates from the origin point of the object, so even though the edge of the object is 82 pixels away, the center is still more than that, so it won't turn on.
You mentioned you'd accounted for the radius of the shield, but I think you need to also add the radius of the object you're detecting for, which may be difficult if the objects in your family are different sizes. You may need to either detect different radiuses separately (which unfortunately means not using a family), or just go with the largest radius and have the shield turn on earlier than normal sometimes.
<img src="http://imageshack.us/a/img189/4411/works2.png" border="0" />
<img src="http://imageshack.us/a/img541/1527/works3.png" border="0" />
Edit: Thanks for checking out my blog!
And yeah, kickstarter can be a hard market. I think we may try again though. To be honest, our campaign wasn't great the first time around, we didn't present anything nearly well enough. Good luck on your own when it comes!