Starting a 1:4 model of an "8x8 tiny house"

While looking for plans for the most simplistic houses around, I found this plan as a PDF of a 8 by 8 foot tiny house from Tiny House Design.

I'm building a ~1:4 model of this house, following these plans. I'm making a few small changes (e.g., I'm building a mirrored model) but I'm trying to stick to the methods used when building bigger houses with this construction approach. The end result would fit in a 60cm by 60cm by 90cm box. The closest I could get mini-lumber to the "2 by 4" lumber that is commonly used in construction was 12mm by 18mm wood, so I'm using that as my mini 2x4s.

For now, the floor framing and three of the four walls are ready, as shown by the following picture.



At the front is a wall with a door (the model door will be 20cm by 50cm) and a window (20cm by 20cm), there's a wall with no windows leading to a back wall with a window. There'll be an extremely small living room at the front of the house (think of it as being 1 by 2 meters in it's real size). A model of a small kitchen and wet bath will be installed at the back of the house. A triangular roof on top of it will house a small loft where one person could sleep.

I can only spend a few hours, every few days a week on the model, so progress will be slow but steady. I'm really a newbie when it comes to constructing something straight and sturdy in wood, so the learning curve is currently hitting me, but I've already learned a lot about construction using wooden frames while working on this little project. Bring on the experience points, I want more and I'll need more when I'll move closer to having to build the triangular roof ...