Ah, I seem to have created confusion. The mdf was cut by a company at Shepperton studios that specialise in that, its not my workshop. I just produced the Cad drawing.

My workshop was my father's hence its at my mother's house.

2mm ply is not that unusual. If you consider a standard .8mm veneer that makes for 1.5mm 3 ply plywood.

AIUI a lot of instruments have wood in the 2mm-3mm range. I believe the ribs of classical violins, cellos and the like are usually nearer 1mm than 2mm. Of course this plywood is a good bit stronger than solid wood as used in high quality instruments. So, yes, its plenty strong enough for the sides, and back too. My #2 is also 2mm ply ribs and back, and about 3mm solid spruce soundboard, and it seems plenty strong enough to knock about.