I was thinking of doing a ramp this way since my boys will not use an open one. They will go through tubes and tunnels though, so I thought maybe this could work. I know you have to secure it to the top level, but is there any type of support needed along the tube. It just seems it would be really flexible and bend while the pigs travel up.
Mine is supported by a screw through the pipe and into the wood base of the second level. you could use zip ties though, either wrapping then around the tube or by punching a couple of holes in the pipe and threading them through there.
The pipe doesn't need any support. It's a little flexible and will bounce a bit as they walk up and down but that has never bothered my GPs.