I thought we just covered that. Those cars are not proportional either. Look at the Tx. Painfully resembles the palm runner.
If you want a cheap Mini-z, go to ToyEast and buy the LXX clone. It is proportional, and is a Mini-z. Same moulds, just cheaper plastic. Shipping is like $30, but the car is only $28. If you can find a bunch of people to buy with you it'd be worth it even with the steep shipping.
Here's a link
http://www.toyeast.com/subcatlist2.asp?catid=1037