The mounts for the original kit, the Hara and Surikarn kits, and even the new molded S-model are aluminum.
My interest in the full-kit mounts is that they appear to offer very good access to the motor screws. Having run shaft-drive cars for the past couple of years, one of the things I was looking forward to in the Cyclone was the cleanliness of the motor-mount design.
Looking at the new tub-S kit, it doesn't seem as smooth as the originals, so I'd like to have those parts on the shelf when I go to build the low-end kit.
Now, given that the total cost of the tub-S kit plus the 3 bulkhead kits would be cheaper than the full-blown kits, why not just do them all the first time?
The plastic SHOULD be lighter than the aluminum. It won't be as rigid, but I want to evaluate the car without them first. If it looks like it really needs those parts, I'll gleefully swap them in later.
AFTER the BMI chassis kit!!