Turned out slightly more complicated.
One of the screw holes on the board (front left) is further away from the edge of the board.
Also I'd forgotten you need access to the front ports - duh !

So I ended up with an interchangeable back piece and seperate left and right front pieces.
Kept the single circle intersection idea.

I did contemplate adding 'puzzle' connectors to the vertical walls.
But the right hand side will have the ssd screwed between the two parts to strengthen that and the back will have a power supply screwed on which will have a similiar effect.
The glue should be sufficient form the left hand wall.

Currently printing the front left piece.
using 3mm walls and base. claims 68gms for this piece. 88 for the back pieces. So total weight of the case alone should be around 312 gms.

have jut thought of a way to interlock side walls. Hmm, back to openscad !
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