Nick, you' re right, they are produced by some type of heat treatment - possibly vacuum forming. I have had a number of discussions with Mark Waring on this topic & I have been trying for the past couple of years to find a company (similar to Just Dashes) here in the UK that could refurbish or reproduce dash tops, knee pads, arm rests, etc but have not come across any to date that can produce these in limited quantities to a high standard for a realistic price.
Andy
' 69 911E---------->R
* Belated congratulations on your recent (' 67 S) aquisition - I admire your optimism ! - I' ll keep my eye out for some 4 1/2 x 15 Fuchs for you.