wheels
 

thinking about losing the Honda civic disc wheels for some ultra light Kosi wheels will there be a loss or gain?

Probably a slight aero loss, unless you have smooth wheel covers over them. If the wheels are any wider, you'll have a substantial aero penalty from the width as well.

HCH wheels are pretty darned good, and if you need new wheels for some other reason, how about some first gen Insight wheels?

2nd generation Civic Hybrid's have a 5 bolt wheel and if I am not mistaken you have a 2nd gen hybrid, so early Honda insight wheels will not work due to them being 100mm 4 bolt wheels, onyour car the wheels that came stock are most likely the best you will find, you might save some weight with ally lug nuts but that is about it.
Also, if you get a chance can you weigh one of your wheels? if you have new or almost new tires then subtracting the tire weight would be ideal, that bit of information would be good for people who are looking for better wheel options or want to figure out how much unsprung weight they would save.

What is your average speed per tank? Its a data point on SGII. If your average speed is less then 30mph then loosing weight is really good. If your average speed is greater then 40mph per tank (Lots of highway driving) then you want the best aero setup you can afford (or live with because of looks).
My commute is 22 stop lights in 5.5 miles so my average is in the 20mph range. I'm spending the majority of my effort on weight loss. I got old honda VX rims to replace my steelies. Saved me 5lbs per corner. That's 20lbs of rotating mass which is worth more then 20lbs from the trunk.