The Insight uses rims with the same specification as the civic.
14"x 5.5" with 45 mm offset and 4x100 bolt circle.
Many aftermarket civic rims that are 14"x6" with 48 mm offset and 4x100 bolt circle also fit just fine.
Look at the photo gallery section on this web site for several photos of various different rims on Insights. Also keep pressing the refresh button the main page and the top banner photo will keep changing. http://www.insightracing.ca/
The Insight rims are already _very_ light. There are probably aftermarket's that are even lighter but the difference will be smaller vs. a "heavyweight" rim. And simple weight reduction as a function of MPG is also only one small part of the equation.
Its usually better for the driver to shed a few of those extra pounds.
No trailer towing going on here. True, brake cooling would be reduced however, riding the brakes isn't conducive to good gas mileage therefor I don't. In a racing application such as the autocrossers here I would remove them. As a mater of fact aren’t all caps illegal in the autocrosses?
Actually the ones to fit 13" front wheel drive hubs are $95.
It actually looks like the ones Todd has are machined aluminum, not the chromed alloy on the website.
I'm still waiting to hear back from him if the ones on his car are actually the same 13" FR wheels on the mooneyes site. But if I had the choice I would take machined aluminum over chromed alloy! For weight and probably price.