20" x 10" Artists Blank Canvas

My first impression was good. It is less deep than other canvases but suitable for my needs and the perfect size ( or so I thought ) .I spent many hours completing painting and only when I came to put it in a shadow frame ( that I purchased especially made to order) did I notice that the canvas is not square! The centre of the canvas from top to bottom measures 9.75” whereas both sides are 10”. I can confirm that a quarter of an inch out looks horrendous in a shadow frame!!!! This has obviously been made with warped wood. I am now left with a painting I can’t mount and a £35 frame I can’t use. Annoyed does not begin to explain how I feel about this situation. The photo shows the light showing through the bow on base of the canvas frame.

Arrived broken