Thank you for your input. While Americas Overland was not written specifically for the motorcycle community, topics covered that would be relevant include pre-trip planning, document preparation, Life-on-the-road advice, border crossing information and documents, shipping information and travel anecdotes. There is also camping information which may or may not be useful to motorcyclists.
By the way, when we were on the road (in our vehicle) in South America and Africa, people often asked us if we had used Hubb as a resource so non-motorcyclists use it as well. Kudos to Horizons Unlimited!