That top end bit with the wings looks like it's designed to turn....
On my Bosch one the door just about stays down, but a flick with your toe and it comes up.
As Above, yours is missing a 19mm slab of chipboard door at the moment, is it not?
"
. For example
a 2400mm × 1200mm × 19mm panel will weigh approx-
imately 36kg
"
so 600 sq would be 36/8 = 4.5kg.