Making your own cage doors

[Pingu]

So, yesterday I received my alexander cage. The problem I find with cage manufacturers is that they don't use the cages they design, so the small tiny doors are always at the top and the large ones are at the bottom. Usually I would redo the cage and use the large door at the front, but with the alexander it won't work. Does anyone have any tips on making their own larger cage doors for their cages?

Many thanks in advance