I don't understand why people want a solid sandbank tunnel.That is a different obstacle.
If you want a solid half-pipe to bank, design and build a solid half-pipe. Coat it with an appropriate surface for grip so their feet don't slide out when the bank. But this is a *unique and new obstacle*
Otherwise, let a tunnel be a tunnel.
You don't campaign for longer contact zones when your dog flies off the top, you train a proper contact so your dog is safe.
Similarly, you don't campaign to make a solid pipe of a tunnel when your dog can't run it in a safe manner.
Not every dog is a fast BC type. Taller than 24" dogs have to learn how to duck and run. Little dogs need to learn to feel safe in this crazy envelope tube. Fast dogs need to learn how to go fast *safely*. Just because people ignore actually training tunnels because their dog just runs through them, does not mean they dont need trained on safe obstacle performance just like anything else.
When I tried an "actual in person agility class", the instructor had us doing full height teeter day one of first class ever, no bang game even. Most dogs spooked, mine I have done lots of work body awareness, balance, and moving things under her feet, as well as she has no noise sensitivities, so she did it fine. That doesn't mean she knows how to do a teeter safely just because she did it correctly immediately. Same with tunnels, just because a fast dog runs through it first try no issues, does not mean they know how to safely perform a tunnel.