Hi Willie,
I’m a bit unsure about this one…can we say that you want some kind of mudguard for those parts of the freewheel which are not covered by the belt?
If yes - just why not try?
But for the lifetime of the freewheel’s inner parts the presence of a sealing will be also important - did you notice this post by Bietrume?
Re: 2014 plastic freewheel interior view
Do yours have sealings?