How to create an ellipse?

I want to create an unfilled ellipse in a shape layer. I first created a filled elliptical shape. My intent was to then create a slightly smaller ellipse and use the subtraction feature which would result in an ellipse with the desired border thickness. The problem is that it is VERY difficult for me to get the precise shape and position prior to releasing the mouse. Once the mouse is released, it appears like no further modifications of the smaller ellipse are possible.

1. Is there a way to change the position and size (of the smaller ellipse) once the mouse is released so I can improve the precision?
2. Is there a better way to create an unfilled ellipse (or any shape for that matter)?

Thanks.

DM

1) yes. Use the path selection tools.

2) Yes. Turn down the Fill slider on the Layer Palette to 0.

Mathias