I finished building the majority of the case, the bending of the side was a real pain in the *** so i had to change tactics a bit. I glued everything in place with PVC glue and hot glue for extra support. Because of that it's not pretty on the inside but it doesn't have to be.
After that i sanded the sides a bit to hide the crimes and used Skotch Brite to give the case a better look.

Because i'm now using hot glue i had to change the dimensions of the construction plate by shaving 3mm off the edges, this doesn't affect anything else.

By doing all this it's now a really sturdy case that will not break any time soon. I used black sticker sheets (used for blinding windows) under the front plate, i think it looks pretty good. The portable feels really good in the hands and the buttons are at the perfect spot.

(This is the sticker i bought, it's used to blind windows and it comes in many paterns and some even colors, i'm glad they had an even coloured black one. I bought this at a hardware store)

(I still need to cut away some of the sticker so you can actually see the screen when it's installed)

Next thing to do is drill all the holes on the edge for the USB connector, charging connector, volume control, shoulder buttons and SD-card access. I also need to drill some holes for the speakers in the front plate and connect a potentiometer to the amplifier. After that i can install everything in the case and it's done.