I saw those, I was just thinking that those huge calipers would add to much weight up on the front wheels rotating. Going to do a bit for research into themI'm not up on it, but I believe there's a disc brake conversion using parts from a Toyota model. Some Internet searching may find the needed info.
I was thinking about rotating mass, probably not that big of a deal. definitely getting rid of the drums in the back for disc brakesLarger rotors would add to the total sprung weight, but perhaps not a great deal. Unless you're track racing it, I'm not sure whether it's worth doing. A rear disc conversion may be worthwhile, as discs all around provide excellent stopping on the Z cars.