Dog in Cargo: Flying JFK to FRA

Anyone have experience with dog in-cargo? He can squeeze into a soft-sided carrier, which might make the United flight possible. JFK-Germany.

1.) Has anyone used everyYay dog kennels for in-cargo travel? Are they sturdy? Do you know alternatives to Impact kennels (which are incredibly expensive)?

2.) How strict are the gate attendants about soft-sided carriers?

Thank you.