On the later model Harleys every trike manufacturers swingarm attaches to that same pivot point, the swingarm shaft, which attaches to and through the rear of the transmission case. This is also where the stock Harley swing arm attaches and is the only option when installing any trike conversion. Its the design HD uses and I have to agree that if there is a weak link, Harley provided it in that design. In all fairness to Champion, there are many thousands of their Harley conversions on the road and I from what I know this is a very rare occurrence. I have never personally seen one crack but have heard of one other occurrence reported here on the forum.
I talked to Champion about this a couple of months ago when the other post was made and they say that it appears that the different cast aluminum trans case batches may not be 100% consistent in their strength because tiny air bubbles were visible in a cracked case that was sent to them for inspection. I'm not sure what year or model the bike was in that instance, it would be interesting to know.
BTW, the other person who posted about this was from New Jersey. Ive been there a couple of times when I helped a friend move to Alabama. Some areas are pothole hell from what I saw. I ran into a couple of 'em that about tore the front end off my truck, so a harsh environment might be a contributing factor. If the rear of the trike did experience severe jarring from hitting potholes over an extended period of time, it could be stress cracking the case and eventually result in failure. I cant see how anything short of that would cause this problem. You may want to ask your friend if he remembers hitting any major potholes. If he did, repairs should be covered under his insurance.