How can I make the nose (or tail) of the fuselage bigger than a single point?
You can, but if you do that you’ll have a transparent hole. Austin hates the way these look, so he won’t let you do it. If you really have a need to do this (like you’re going to cover the hole with another part) there is a workaround. First create the cross section you want in the adjacent section (e.g., one section back from the nose). Then use the “Copy Sec” arrow to copy the section profile forward to the nose section (or back to the tail section). Now you can set the second section to whatever you want it to be.