2915-1 box help needed

Hi, help needed - I’m planning on making an insert for my 2915-1 watch box. I have the box but no insert. Is it considered bad form making a replica insert - is it acceptable? Perhaps I won’t start the project if it is considered wrong.

My problem is I don’t have an original insert to study. Any chance someone who has access to one could post the dimensions and a few images that show the insert top, sides and underside and images of any details that show construction and materials - it would be truly appreciated. I’ll post progress photos here if the project gets underway.
Many thanks

Nothing wrong with it if disclosed when selling. I love this red box and here are some pictures I have on file with closed-up detail of the insert. Unfortunately I don't have any photos that show the underside.

Thank you so much for the great images - this will be a huge help. I’ll post some images of the project once started. Any chance Incan get the dimensions of the cut out and dimensions of the location from each end - thanks.

All so, what is the insert frame material made of - is it normal cardboard or something else - thanks