Considering the recent spate of electrocutions - mostly of pets - involving energized handhole covers, I think it's time to consider this a 'must do.'
Especially since you use the metal covers when you need a 'traffic rated' cover.
If it's any help, these covers invariably have some angle iron on them - a convenient place to bond. Or, the metal is plenty thick enough to support screw threads. (Just don't use long Teks screws; you don't want to go into the flat tire manufacturing business!)
