Good stuff. I want to modify my trailers (one in each home) to carry my dog. I hope she likes riding in it. The trouble is that she's really tall. She's very small for a greyhound, but that's still taller than most dogs. She's 25" tall at the shoulder and probably more than 36" from nose to base of tail. I think she needs at least a 30" by 36" rectangle to lie down. What are the dimensions of your flat beds?

Of course, I would build walls and a harness for my trailers.