If you could fit what amounts to a strip of stainless steel in there, as you can, it has to be better than the chain whacking the alloy or mag housing if it breaks!
When my mate Adrian gets back from his holiday in France I have a list of jobs for him as well as bits for the Minitwin bike I also have aengine case protector on the list and as I have a left engine case sat on the shelf it shouldn't take him to long to come up with something, afterall he works in a Sheet metal workshop