Do aluminum shafts (C4 specifically) have the strength needed to act as a suspension member though? Seems like they can handle the torque from high power C4's, but I dont know about compression loads. The Denny's aluminum shafts for C3's are probably thicker walled and use a higher quality aluminum, but are also probably twice the cost of what you could have some used C4 shafts cut to length for.
absolutely, a short shaft even in aluminum can take 3500 pounds in tension as well as compression. That's the whole car standing on it or hanging by it.
In reality none of us would see even half of that even if you could pull 1 g in a turn.