When I was in college --a gazillion years ago-- my father invented a kitchen bread slicer. It was really just a fancy miter box for a loaf of home-baked bread but it worked really well. You could slice it up and they'd fit in a toaster.
He got it patented. He had a mould built. He had plastic company begin production. They were functional and came in bright colours and were a hit.
And then Rhodes Bread company started selling clones. He met with his attorney and learned the facts of life. It would take more money to fight the infringement than he had.
Over the last several years, I've bookmarked teardrop manufacturers on my web browser. Most of those links don't work anymore. They went belly up. If you look at successful (quality) manufacturers such as Camp-Inn, So-Cal, Inca and Vistabule to name a few, they've figured out how to market quality products. And since I don't hear about problems, they must stand behind what they make.
Googling around, I see that Alto Travel Trailers has a patent for their roof expansion system. What I can't find is a patent for Camp-Inn's unique Raindrop. Nor can I find one for Vistabule's galley windscreen or any of their other innovative ideas.
So-Cal isn't copying the Raindrop. Camp-Inn isn't adding galley windscreens.
I think what survives (and sells) in the commercial teardrop world is
quality and customer service. Build your unique teardrop. Build it right and treat your customers like good friends and you'll do fine.
Tony