I saw them in person a few days ago very nice rays. I use the same heater before that you have and I never had a ray get burned. That mark on the rays back kindof looked like it was bitten by the other one when I saw it. I would just put some PVC piping around the heater and drill holes in it. This I what I think would be the best for not getting heater burn.
Like this one
Like this one


