I'm just throwin this out to ya..
Rota makes a 13x5 wheel thats super light..
If their 15x6.5 weights 11.9lbs each, those 13's have to be 10 or less.
And the nice thing about these is, their very inexpensive..
I have 16x7's on my truck and they weigh 13.9lbs each..
Stock honda center caps snap right in as well..
http://www.rotawheels.com/slipstream.php
and you can see the weights here..
http://www.wheelweights.net/
just an idea..