I have followed this story with interest from the beginning -- engineering disasters are a fascinating and informative topic -- and the number and variety of terrible decisions are seemingly endless.
There is the story of the connector rings that held the end caps to the hull, not mentioned here, but a disaster waiting to happen all their own.
There were these two metal rings that connected the hull to the end caps, using epoxy, built for the first hull. When that hull was scraped to save money Rush reused them. Only problem was cleaning off that epoxy. There was no approved method of removing the epoxy such that the surface could be rebonded later. But Rush just had his engineers work out some way to scrape it off. So the seal on the rings was not based on any approved and tested bonding process. Worse still, the rings were not requalified for reuse, they were just reused as is without inspection or testing.
It gets worse. Much worse.
The rings were designed and fabricated for only one thing -- holding the caps on the hull. Rush got impatient with his sling recovery system and decided to lift the sub out of the water using hooks and lifting rings mounted on the sub. But there was no provision for mounting lifting rings on the sub. No problem, Rush had lifting rings welded to the hull cap rings.
Not only is just welding a couple of lifting rings to the cap ring a disqualifying alteration of the part simply by doing it, but the use of the hull cap bonding ring to lift the weight of the sub was just insane.
There was a seemingly an unending series of defiantly stupid decisions being made. Every "breaking all the rules" move he made that did not immediately result in disaster justified in his mind breaking even more. As with the launch managers of the Space Shuttle with the cold O-ring problem, each launch in below guideline temperatures without a disaster justified launching at still colder temperatures. Keep this up and you will eventually find out exactly where disaster lies.