Tremolo between notes obscures natural accidental

The measures pictured are in key D major. When I added the tremolo between notes 'A' and "C natural", the natural symbol was very difficult to see, obscured by the tremolo marking... Not knowing how to remedy this, I used the Inspector to HIDE the natural mark on the 'C', and added some staff text to tell the player that the 'C' should not be a sharp, but a natural. I don't know how else to notate this situation. Any ideas? Thanks.