Finally had these made today!  This is the first design I had in mind.  It is the easiest one to machine and the weight savings are quite good.

If you want to read about the different designs go here: Spacer Design
 
Picture 5942
 
Surprisingly the 10mm spacer came out weighing less than the predicted weight by .6 grams. 
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Comparatively a 10mm plain carbon fiber spacer weighs in at 5.2 grams. 
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Here are the weights of the 20mm and 5mm spacers respectively.
Picture 5930 Picture 5931
 
And here’s how they stack up. 
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