I never realized, until a few days ago, what effect my arm against the soundboard has upon sound from my teardrop f-hole instrument. Here is my solution (see below):
Ingredients: Bolivian rosewood scrap, bamboo, lashing material, leather, contact cement, epoxy, ...........patience. Getting a precise cut for the jaw opening took a few tries. It's easily removable but stays where it's supposed to. Admittedly, could use a bit more finishing this coming weekend....
The bottom, where the bamboo is epoxied, has a relieved section (carved with Japanese carving tool) for better fit and mechanical bonding.
The sounds coming from this instrument are much improved.