Yes, HK-4 is was.
My Dad had a coffee table made from a piece of spar cap, 28-ply Birch.
Beautiful wood, superbly crafted.
As I recall, Henry Kaiser pulled out of the project due to his doubts about Hughes ability to actually get the airplane built.
After all, Kaiser, being one very smart and successful businessman, who was the prime contractor on Hoover Dam (The Six Companies), completed two years ahead of schedule and under budget, had the noteable distinction of having his company build Liberty ships...4 per day were turned out toward the end of the war.
With all that success, Hughes was seen as a liability, I believe.