The size of my light cone's Tail will depend on what I intend to do with my telescope. If I wish to engage in Astrophotography, I may want to construct a Flip Box that will enable me to switch part of the Tail back and forth between the focuser, and my 35mm camera. This would make my telescope into a very super telephoto lens for my camera.
The required light cone would have to extend 42.4mm or 1.67" into my camera after crossing the Flip Box. The Flip Box must be wide enough to accomodate the focuser and all its mountings and knobs. For this I will need most of the 10.75" of the Tail provided by a 2" Flat.   Where you place your Flat is up to you. Hopefully I have impressed upon you the importance of this often overlooked component of your telescope.