Protection plate for bluetit next box

Hi there, I’m after some advice. 
I have a bluetit currently on Day 9 incubating 8 eggs. It’s a camera box. 
In the last 2 days we’ve had a persistent woodpecker showing a lot of interest in the box and on the entrance hole. 
My question is am I ok to add a protection plate whilst she is incubating? Will I frighten her off? I would have to climb the tree and screw one on? At the moment I am shooing him off and have taken anyway his daily peanut supply to deter him from visiting. I am currently waiting for a 25mm plate to arrive in the post. 
Many thanks

Paula