I've had a bit of a test making a mulching plate to use instead of the chute on the mower, the blades appear suitable for mulching. It started out easy with me just whacking a bit of sheetmetal over the hole and two pop rivets at the front and one behind, as well as an extra plate on top to cover the hole. Instant fail.
Then I tried an extra pop rivet at the rear to strengthen it. Slightly slower fail.
Hmm thinks a bit more about it and decides to put an extra plate inside to stop clippings being wedged into the rear where the pop rivets were stressed. It seems successful now but early days yet.