In one embodiment, an adapter for increasing exterior dimensions of a post mount support block includes a base having two sides that meet to form an angle of approximately ninety degrees, two legs, wherein each of the two legs extends from an outside edge of a different one of the two sides of the base, and two flanges, wherein each of the two flanges extends from an inside edge of a different one of the two sides of the base, such that each of the two flanges is positioned in a substantially parallel orientation relative to one of the two legs.