This has never been discussed. Everybody has been boasting about their magic brakes and lately hydraulic caliper discs.
So here is my boast about the oft derided Sturmey Archer 90 mm DRUM brakes.
Yesterday in extra warm perfect road conditions with NO traffic, on the flat bottom roll out of a short medium steep curvy hill near my home.
I was going 39.9 mph and tried to pick an exact spot on the road and pulled the levers hard.
I stopped, then turned the bike around and counted how many times the 700 x 36c tire went around to the assumed start of braking. There was NO skidding of either tire and only a slight lift of the back end at stop. I didn't change my normal sitting posture either.
It appeared to have been 6 or 7 turns, set at 2170 mm. So 42 to 46 feet, I think it was more like 42 feet. I would need a spotter to get it down to a 4" error.
My front tire is a low miles but 9 year old Schwalbe Marathon city tire.
Bike is a steel 41 lb roadster with about 7 lbs tools and drinks.

So now post what YOUR RESULTS ARE. Let's see IF your brakes are actually better than my SA DRUM brakes. LOL.

https://www.google.ca/maps/@53.53209...!3m1!1e3?hl=en

That is about 1.25 g.

How did you not endo?

Are you sure it wasn't 29.99 mph?

This Sigma 14.12 speedo is wired and rollout set. Accurate to 30 feet a mile. I could get it set closer. 100% reliable and repeatable.
Unlike bogus GPS wireless strava gizmos.
I didn't feel any Gs really. Where that comes from, I have no idea.
I don't endo because my drum brakes act BETTER than pulsing anti-lock car brakes. Friction is in the hub.
Sorry you don't think good brakes are POSSIBLE. LOL. Hilarious.

What you report is absolutely impossible.

At around 0.8-0.9g, you will go over the bars.

I am not disputing that SA drums are good brakes. The are. I am not even disputing your data because it is clearly very hilarious as in ridiculous. Maybe 65 feet is believable. The limits to stopping on a bike on dry roads isn't the brakes.

Key point. You can slide back very far on the bike to keep from going over the bars, but the back wheel will still skid. If the OP wasn't skidding the back wheel, maximum braking was not happening. And "maintaining normal posture" is not a test of the brakes but of whatever the normal weight distribution is.

It’s good you showed pictures of your bike. You have a few advantages over the typical bike which may work in your favor. The mirror clearly acts like a wind brake giving you a major advantage. Also your upright position and extensive cabling ect. assist with aerodynamic braking as well. Perhaps a good option would be to find a long very steep hill perhaps 5 to 6 miles at 8% or so and see how that goes.

This is a non-sequitur. Whether the "endo" happens or not has nothing to do with where the friction occurs.
It depends on the relationship between the center of mass of the bike-rider system and the axle of the front wheel during brake application. If the center of mass projects through or below the front axle, endo will not happen. It depends largely on how far back you can position your keister.

Going over the bars will also depend on the force applied on the front brake vs the rear brake.

You can not fly over the bars with braking only on the rear. If the braking force would reach the point where the rear wheel comes off the ground, then one is no longer applying braking force, and the bike doesn't flip (assuming the rider stays on the bike).

Marathons should be fairly grippy tires for the test.

I did a similar test with rim brakes a few years ago. Unfortunately I don't remember the exact distance, but the OP's distance sounds reasonable. In my case, I laid quite a bit of rubber down.