Keith, I am using a similar box file at the moment. I used both a knife and saw to ‘deconstruct’ mine. Be aware that the more you cut off, the less rigid it becomes of course. I am getting towards the end of the construction stage and fixed my track to ply a little smaller in dimensions than the file. This avoided the bottom going soggy - cos we all know there is nothing worse than a soggy bottom! A smaller ply base allows a back scene to slide into the back and sides. Building onto a ply base allows you to do lots of construction/electrics/scenic work and then you can place the base into the box file. If you want to see my first box file google M & J Brewery Sidings and hopefully the pictures will be there. Enjoy building your micro layout.