Ok, so the fail safe method I use for stomach tubing (lambs and calves, works for both). Your tube is a rigid pipe. The lamb has a windpipe (rigid) and soft oesophagus which leads to stomach. Sit on a bucket, and hold the lamb between your legs, with his back legs dangling down. Put the tube in the left side of his mouth and let him swallow it down. Then roll your finger over his neck- you should be able to feel 2 rigid tubes. If you can only feel 1, the stomach tube is in the airway. If you can feel 2, it’s gone down into the stomach. Works for calves too. I have a trusti tuber for lambs and have tubed countless lambs and none of them have drowned, just always check for 2 rigid pipes/tubes before you put any liquid in. It’s daunting but anyone lambing sheep really needs to know how to do it.