Quick reply...
1. Because the hitch does hold in both a lengthwise pull and in a perpendicular pull, the test you described could be done either between: 1) using a single (fallen) tree trunk, creating lengthwise pull as I performed in prior videos or 2) between the bases of two standing trees. Do you have a preference for which?
I don't believe it would make any significant different in terms of what we are trying to determine.
That is, the idea is to load the 2 hitches till MBS yield point is reached.
One knot will fail first - and you will have a 'survivor' specimen to examine.
The 'survivor' will have been maximally loaded - and if it can be easily untied, you can pop the champagne cork (assuming no obvious damage caused by heat build up).
When untying the 'surviving' hitch - take note of which rope segments have sustained evidence of stress/crushing. Try to pinpoint where (location) within the hitch where these stress concentrations occur. This is valuable information.
2. Is it acceptable that I do the test with a cordage that is in the 5mm range rather than a climbing line which is double that diameter and much stronger? Because I would need to get much more creative with my rigging if i need to break an 8mm cord instead of a 5mm.
It is always preferable to test with the same type of rope material/diameter that would be used in the field.
This means that you need robust test equipment - with ability to achieve peak load of around 3 metric tons (3000kg).
Using lesser diameter material would serve as a pathfinder - but you need to go full scale to be 100% certain of your results.
3. When you say "the first stage in the release sequence", I assume you mean after the "drawloop" has pulled through the first munter/loop in the hitch itself.
Yes.
Because as you are aware from your diagram, there are 3 stages to the structure of the hitch, but when I am actually executing the release, it feels like only 2.
Correct, only 2 stages.
What we are trying to investigate is whether your hitch is survivable after having triggered the first step of the release sequence (ie how fault tolerate your hitch is).
Triggering the second stage of the release sequence means death or serious injury (if you manage to survive the free-fall).
And so I am inferring you want me to determine how secure the hitch is in an intermediate state, partially compromised, even if such a state would be difficult to achieve in a real field situation.
Correct.
I am hoping that you can see that the default 'pull-it-till-it-breaks' mindset is a dead-end path that doesn't provide meaningful information.
For many knot testers, this is the only way they can conceptualize knots. There are some promising signs that one or two knot testers are starting to expand their mind - and look at other factors (but once a leopard has spots, its hard to change those spots).
However, you can use the 'pull-it-till-it-breaks' mindset in a contest between 2 identically tied knots/hitches - where one will always yield first - leaving a 'survivor' to closely examine. Carefully untie the surviving hitch - and examine which segments of rope have been crushed or heat glazed. Mark these segments (with permanent marker pen) and re-tie the hitch, noting where these segment are located.
and so what would you recommend as the STRONGEST means to attach the test line to my winch in the center, which terminates with a carabiner has a small bend radius? A Palomar? All I can think of is to tie another JRB hitch, perhaps the 3 turn variant onto the carabiners. I don't know which will fail first: one of the JRB hitches on the tree or one on the beaners, but would guess the latter. What is the strongest hitch for attaching a carabiner? The 'hitch to beat' in terms of strength?
One of the key concepts with all types of testing is to engineer out any experimental bias.
Eye knots are easier to test (obviously) - but, your creation isn't an eye knot.
Have a look at the attached image (extract from EN892).
Note how the rope is terminated.
I suggest that you try to adopt a similar method of terminating (but more turns to create a 'capstan effect').
A large size shackle with 30mm diameter pin would be okay...
Edit note:The image is fair use under copyright laws - it is just one small extract.