[gpetilli]

It looks like you have a very rigid bearing support behind the flimsy sheet metal. Can you extend that? How close are you to the 120" frame perimeter? Reminder - you are only required to have bumpers on 8" on either side of a corner, so you don't have to protect the middle wheel if that makes things easier. You do need to add at least 1/2" of rigid support at the edges of each bumper segment. Again, it looks like the wheel side is fine without the extra sheet metal. If you are concerned about the bumper rubbing on the bearing or axle, you can add a small relief in the plywood at that point.