Whatever you have to do!

The scale is wrong on mine too--not that you can get it perfect anyway. It's still too tall, but if I make the top of the car any smaller, you can't get into it.
I was thinking about putting sidewalks beside it to artifically lower the height, but your clip idea is much better

To scale mine, I resized until the wheel looked about the right size, and then based the size of everything else off that--the hood is 1.5 wheel widths, the chassis is raised above the ground 1/3 or one wheel diameter, etc. Even after all that, I still reduced the size of it a couple of times to make it all look right!

If I had this to start over again, I would make a simple boxy shape of the car's dimensions as best as I could judge and acertain an approximate length/width. Then I'd scale a custom texture of the car's profile to those dimensions, and just "cut out" the car to get the right shape. Too bad I didn't think of that before!

Anyway, enough of my ranting!