Yes the tunnels are secure I would never let my little piggers get hurt... they have 4 wire ties in each holding it in place, they arent visible in the picture because they are yellow and I have OCD and need things to match ha ha.
VERY NICE. I used to have a wooden ramp with felt on it for the piggies to go to the second level. Alot of them were to scared because it just seemed a little steep for them because they are VERY SMALL for their age. I used that black gardening tube that you used for your ramp, and THEY LOVE IT. Even the littlest pigs go up the tube. It's easier for them because there are like ribbed circles in the tube so they can grip so much better than a regular tunnel. I poked a hole in every other dip on the side and cable tied mine to the grid and laid the tube on top directly of my old ramp so they knew what it was. GREAT IDEA. Im so happy you thought of it. For $2.00 I have a Ramp in all 4 of my cages that the piggies love.