Actually, you are both right. There are two version of the 3G RX-7 rims. The first ones on the earlier cars were lighter, but turned out to be prone to cracking. The later version didn't have the problem, but weighed more. Aside from the weight, there was a way you could tell the difference by whether the backs of the spokes were sharp or smooth, but I can't remember which was which. Look at this link near he bottom of the page:
http://www.scuderiaciriani.com/rx7/wheels.html


juan