Mad_Jock,
While you've got a CNC machine making these things, you may as well score a mark every inch and a half or so (is it?) to denote 10nm on 1:500 000 charts too.
By the way if you end with non-slip material AND a tourniquet (aka. strap for leg) then is it possible that you won't be able to move your legs at all?
Perhaps we should nonimate a name for the product - 'Jockboard'?!