Tank tread bumpers?

[Ichlieberoboter]

My team and I were thinking about doing tank treads this year so we could get over some of the defenses. We wanted to do something like this. We were wondering, though, about how we would position our bumpers for it to be legal and how exactly that would work. We had a couple ideas like replacing the pvc with rubber and maybe forcing a bike tire around some of our hard wheels as a track, but we are still very unsure of how we would accomplish this.