I personally would not attach another cage with a pvc tube , nor would I use plexiglass as removing wire can prevent air flow and thus raise the temperature in the cage If you want to entend your cage how about the 'attic extension that John Hopewell makes which is far more 'chin friendly
John Hopewell (Marketing) Rotherham South Yorkshire, Chinchilla Cages - Degu Cage - Degus Exercise Wheels - Cages - Animal Cages - Rat Cage - Ezi-Filla - Ezi - Easy - Automatic Water Drinking Systems - Guinea Pig Runs - Rabbit Feed Hoppers - Birds -