This is a very interesting thought process, So how important is it to even out the weight on the back wheels?
However these cars with the 3:2 weight distribution have done well for us.
The answer to your question, ....how important is it to even out the weight on the back wheels? The answer is I don't know for sure. There are so many factors that have an effect on the car, that how the rear is weighted may/will change based on all of the other factors involved. All a person can do is develop a hypothesis and then test to see if you are headed down the correct path.
Your cars that have done well, may like the weight bias you have based on the COG, amount of steer, COM, and wheelbase.
I am going to repeat this: Everything on a build has some effect on everything else. Keep this in mind as you are working on your hypothesis.
Yes, I find this discussion interesting ...Good Luck.