I'm still not convinced they're fuelleborni.
"Red Top" trewavasae are far more common than any red top fuelleborni variant but it shouldn't be that hard to tell them apart.
The OB's do look more fuelleborni.
I think hybrids are a possibility. It wouldn't be difficult to get a fuelleborni and cross it to a trewavasae. They look so much alike. Some people do it and don't realize it.