If you haven't heard anyone complain about Tom Hennessy's mods, then you simply weren't paying attention. He didn't offer a zippered model until after the Blackbird and 2QZQ were so successful. He didn't offer a two-layer model until other two-layer models (mostly Brandon's) started taking his business. Same as the zipper...he realized other folks' ideas had profit potential for him, so he took his market share back with their ideas.
I was curious. Brandon is the individual who invented the double layer hammock?