Hi Bob -- you might try the Apple Aperture discussion group hosted by Apple
-- it's a helpful and knowledgeable group (I post there regularly).
I always keep the Intensity setting of the Edge Sharpen Brick to less than 1.0, usually close to 0.75. This is more personal choice than anything else (in my experience over-sharpening sets in quickly, and so I always under-sharpen).
I almost always print with Sharpening turned on and set to Amount = 0.29 and Radius = 0.29.
But note that I'm printing matte with an Epson 3880 on their Hot Press papers (I like the surface of the ink).
None of the above has been even casually tested. I found settings that work and haven't experimented with making them better.