this is the roof section. FYI i used Krylon Fusion spray paint ( for plastic and PVC )

I would probably line the end and even the top with wire like welded utility wire or panels of concrete reinforcing wire. Squash seem to like the smaller wire to wrap their tendrils around. I tihnk the fencing would be better than netting (and stronger too).
I think I would also put maybe 2-3' chicken wire around the tubs. Don't you think the animals could easily reach on top of the tubs/containers and yank them out or chew them off from the ground? Also, once the squash start hanging down, you might want to support them with something like nylon hosiery, so they don't break off. Good luck!

P.S. I also wanted to add that you might consider using 4 metal stakes pounded into the ground at each corner and attached to your PVC pipe, just to stabilize it, should you get gusts of wind. You could just attach them with tight bungee cords.

Thanks forur input...I was thinking about drilling the PVC and sliding in some thin metal dowels to reduce the open spaces by 50%...then the trellis netting. Also, i plan on driving some re-rod bars into the ground and will slide the PVC over them. Lastly, on the 5gallon bucket side of this trellis/arbor I cut an additional 1 ft off the verticals....so it will slope me towards the sun and not so high for the squash to climb b4 it makes it to the roof. I will post pics if desired when it is completed. Have a great Spring