I did add a note pointing out this will effect the overall size, but in all the buildings I have built it only really means taking 1mm - 1.5mm off the internal floors. The small engine shed has no internal floors so makes no difference.
These kits are fine if you want a quick fix, but it means you do not have anything unique. I use them as an alternative to building from scratch i.e. use the basic shape and frame and enhance as much as possible to make it better.
Of course you can just colour the edges, stick a drain pipe on the corner (not very prototypical) or fill in with extra card (ending up with two cut lines to hide), everyone has their own favourite solution, tried some of these myself, but I know which i prefer.
The other thing I do not like about Metcalfe kits, are the printed roofs, I think every single kit I have bought has the same bland colour roof, which I always cover with Scalescenes Slates or Tiles.
Here's a pic (work in progress) showing hidden corners, Scalescenes Tiles and Flashings, added gutters and drain pipes, scratch built smoke hood covers, lamp, and bell box, with doors converted to working hinges (with maybe a view to solenoid operation)
Now working on internal details and inspection pit, etc
And I need to weather those window frames!