What confers additional stability to double helix model of DNA apart from the H-bond?
One base pair provides inductive effect to the other.
One base pair is stacked over the other.
One base pair is perpendicular to another.
One base pair interacts with another base pair via steric hindrance.
The plane of one base pair stacks over the other in double helix. This, in addition to H-bonds, confers stability of the helical structure.