We have a Problem Houston

We have a Problem Houston 
The jigsaw we are currently doing is 'The Starry Night' by Vincent van Gogh. The puzzle is quite difficult. All pieces are the same shape and size. The puzzle is split into 6 sections. Each section has letters on the back telling you which part they come from (Thank Goodness). I have just complete my corner, Sue is on her third section :) Now the problem. The jigsaw board we make them on is about 2mm too narrow. If you look closely at the second row in from the left you can see the overlap.