Peter,
I know, I thought I'd post the results of my investigations and the conclusion I'd reached.
There are suitable pannel speakers, but to get the high power handling you need to get the volume needed without any distortion they need solid panels and each speaker is at least £100 - unless you can find a system from a scrapped high end German car! They need to be shallow and waterproof!
Looking at the way the car is built my feeling is that there is room to put a head mount a bit forward of the factory position, in a nice bespoke and upholstered unit so it is immediatly behind the "front" of the hand brake lever slot.
I keep saying no, but I may yet do this. I just don't really want to butcher the dash and for the life of me I can't see where else to put the tweeters!
