The weight of the cars was considered, but we didn't want to modify any of the cars. This was meant to be a comparison of the cars as racers; which car, out of the box and with the right equipment, would be the best choice? As such, a car that is naturally lighter will certainly gain an advantage over a heavier car. The Xray was a good example of that, same with the Losi. The Losi was heavier, and although we could have milled out a chassis to save weight, that would not really be in the spirit of testing the cars as the average person could buy them.
As far as adding weight to make a car "legal" we chose to run them out of the box. I have raced at many clubs and many national events, and only at the large events is weight a real issue. Very few clubs that I have seen spend a lot of time teching weight on a weekly basis. That's not to say that none of them do, but once again, if a car was lighter out of the box I felt that deserves to give it an advantage.
The diff/one-way thing was my pet peeve in the test. My choice would have been all diffs or all spools, since we were at the Tamiya track, where those are usually the choice at the Reedy race. That is something we will learn from and do differently the next time we do a test like this (which will be a long way off).