Wow, first 10.5 post on new board...Here goes, a couple of resons for this, first off there are already a few organizations that run similar rules and weights, and we wanted to accomodate an already existing field. Also, the design of these cars only allow for so much weight reduction in them. The scale we are at now seems to be obtainable for everyone and put them all in the ET range originally desired.
Hope that answers your questions,
Rich