: Can anyone tell me
: where I need to put the apex of the cones to produce bottom
: panels like those on the Point Bennett and Chesapeake 17?

Search out info from Barry, Rabl, or Kilgore.
Depending on the design - even relatively simple ones, there can be many 'apexes' of many cones. In simple terms for an existing design, one takes the 2 views (side and top, say) and draw a ruling line on one view extending outward and that line's projection on the other view outward to the point that their horizontal coordinate is the same. If an adjacent ruling line can intersect that horizontal coordinate and still be true to the 2 views, then move on and see if the next ruling line will also use that same apex. If not, try another apex for that 3rd line. If it works for the full length of the shape, you're in luck- if not, try other ruling lines and apexes. The notion being used is that 2 closely adjacent lines can only be on the same plane (ie developable surface) if they are either exactly parallel or that they intersect.
I have not explained it very well, the big boys mentioned will do better.
-mick