Very interesting numbers. As I said from the start I have never had any direct comparisons to other readings or even owned any lights that I trust the lumen readings on to get readings from. Every light I tried just made things more complicated since none of them seemed to produce the numbers they said they did.
I know it reads inline with most other spheres readings on BLF that I see.
For example the readings VOB got earlier today with the GT XHP70.2 were around 8800 lumens with a sliced dome. My own XHP70.2 readings on the GT were just under 10k lumens with the dome on. Within ~5% or so all things considered. That is what I normally see when compared to others readings.
25-30% is much further off then I expected.
After we see what others get we can come up with an adjustment factor if needed since they are all calibrated the same. I can even recalibrate them free of charge (minus shipping) if people want if we figure out a good number.
What stands out to me are the zebralights being rated the same but getting such different readings. A slight variation is one thing but that much difference for lights so close would say that they are outputting different numbers, which would say that at least one of them is not putting out the 1126 lumens it is supposed to.
Can you try a ceiling bounce with those lights to compare?