saltfever, you seem to be fighting an uphill battle here and you're fighting it by yourself.
I think you're attempting to isolate a single component of something that's designed to function as a system and trying to somehow come up with some kind of supporting data that might indicate that this one single component is an inferior design if it were acting alone. You're not looking at the entire roll cage and chassis as a system. You're mixing up your signals here.
I am not an engineer
Neiter am I but this guy is:
Basic rule of thumb for virtually all structures is that arches and triangles are far stronger than squares and rectangles.
What's he's saying doesn't jive with this:
Anything other than perpendicular is a weaker design.
Back to not being an engineer... The driving force (no pun intended) behind these roll cage rules are engineers. And they're also chassis builders. And their also the first responders who arrive on site after an incident. Combined they have many many years of experience and know what makes for a good roll cage design.
NHRA, and NASCAR conditions don’t exist and are irrelevant.
So drag racing and roundy-round cars don't apply but somehow this does?
If strength is an issue look at the Tractor-Pullers. Cages use vertical uprights.
Seriously? Tractor pullers? Out of all the other mainstream racing facets I'd say the one that most closely parallels land speed racing is the NHRA. The NHRA and SFI have more engineering resources than we'll ever know. I think it's pretty safe to take a page from their book and draw from their knowledge base.
In a crash the loads are very complex.
You stated this yourself but you don't seem to be accepting this fact. They are complex and very dynamic in nature. Every scenario you've described involves apply thousands and thousands of pounds of force directly down vertically on top of the cage. These cars aren't getting dumped off a cliff or pushed out of a low flying plane and landing right smack on top of the roll cages. You said it yourself... the loads are very complex.
This might be the reason why this sentence is on page 24 of the current rule book: "all roll cage structures shall be designed to protect the driver from any angle...".
Any angle, not just from the top. Look at the cage as a system. The front hoop is only one small part of the larger picture here. And I think it's entirely safe to say that the SCTA has acquired enough significant data of the many years of its existence to support the fact that a roll cage with a laid back front hoop is better than a roll cage with a vertical front hoop.
It's as simple as that.
