How do I pair Cut-Extrudes

I need to make a Cut Extrude on one side of a part and to make a mirror Cut Extrude on the other side of the part.  The attached Project shows the Cut Extrude on one side. I produced the cut extrude by inserting a plane at the required angle to the part and Sketching the dimensions of the CE.  My problems are:

1.   I am unable to correctly position the CE on the body.  I can't create any dimensions between the Part and the CE.

2.   How can I make the mirror CE and how do I position it on the other side of the part.

3.   And I should ask...  am I using the correct approach; ie, using an angled plane and Cut Extruding?

Please note that I am using 2010 version.

Bevin

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