I am aware of the 25 foot rule with appropriate subtractions for elbo’s. However, can this be 25 feet vertically? Doesn’t make common sense to me yet I have never read a vertical limit. Is 10 feet up to the attic and 6 feet to the soffit (exterior) within the limits?
Yes it is in the limits. There is no distinction between vertical and horizontal that I am aware of.
It may also vary by manufacturer.