the TC4 chassis is not an improvement over the stock tub other than it's lighter and adds a bling factor. It flexes as much or more than the molded graphite one, but I think it flexes easier one way than the other.
I hope BMI changes the TC4 over to the TC3 chassis they make. BMI TC3 chassis is much stiffer and consistant left to right by it's design. I think BMI just needs to change the motor mount on the BMI TC4 chassis to a BMI TC3 one, so that you can have an even cut upper deck. Personally, I would rather go back to the TC3 shock towers and wing chassis braces, but keep the steering rack and toe blocks. It would be nice to get the upper brace as low on the chassis you can. Just my two cents.