OK - is this what you were thinking? wsDK - weak secondary Dall Kirkham telescope
If you fold a Newt back through the primary with a flat you are automatically folding over half the focal length, which in turn means that you need a flat that is OVER 50% of the diameter of the primary. You can do that, but it is not pretty!
The wsDK is the better version. It compromises a weakly curved secondary to get a 34%, plus or minus, secondary size and utilizes a tertiary to give you the eyepiece height that allows viewing without a ladder. (And no hole required in the primary)
Yes; in my post above I gave a link to an article about the US Naval Observatory astrometric reflector. The 60 inch f/10 design required a secondary flat with a diameter of 35 inches.