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closer to a 90degree angle
I don't think they are.
The anhedral on the elbow cup mating surface of the Ventus has annoyed me ever since I got them, but obviously never quite enough to get around to doing anything about it. Any simple solution (i.e. a wedge) has the disadvantage of adding more stack height between the extensions and the cups, and I like the close-coupled cup/extension more than I hate the anhedral. If I wanted to throw a pile of money at it, I have an idea for an epically #tartmode top clamp set with an integral bridge, which would solve the anhedral issue and the twisting about the vertical axis.
Looks like you can use these: https://store.3tcycling.com/en/spare-parts/aerobars/clamp-conversion-kit-on-basebar-164.html
Look far more robust and closer to a 90degree angle