I'm sorry not answering faster, but being in France I'm not synchronised at all with you !
(I just woke up, seeing all those questions and reactions ! nice !)
You're right about how I bend mdf, even if I'd have much trouble to say it myself in English !
" The MDF is run over a saw repeatedly in a uniform fashion to put lots of those cut lines (called "kerfs") in the material. This helps the material bend easily. "
That's it ! the cut lines are 8 mm tall, on a 12 mm mdf.
After that it's glued and maintained squeed for a while.
The point is it's really really cheapper than curved plywood and not viewable at all from outside (the idea is not mine, I was told by a carpenter).
I just should fill the black holes with some "wood paste" for it to be perfect.
The design idea came to me after few experimentations about the usual cab shapes.
I had started working on a naomi-universal-cab-like this summer but then I remember the round shapes of the cab you can see in "Soylent green", the same that acasualtourist uses for his logo

! I had seen it too in an exhibition called "Game On" (really cool) but couldn't remember exactly what it looked like.
Instead of looking for it I went for a few drawings, until I had the one I wanted...
You're right I should bend some more mdf at front kick panel, it'd match better with the drawing I did, moreover it would be easy with 3 mm mdf.
I'll do when I stop working all day long on it, needing some space for my knees !
you see I stopped painting few months ago and now I'm more working on computer-art...
did someone say I should not call himself a "painter" ?

edit : s**t, my animated gif are not animated ! animations viewable here :
http://mixo.matoz.free.fr/arcade_cab/gif.htm