Just and FYI for those that are attempting this approach. I am doing this right now, by omitting section C AND shortening Secint B on the C side to only 2 feet in order to fit my basement. Make sure you change the end part of section B to match the end part of section C so you can finish the end of section B properly. Otherwise you will end up with a missing support for the end of the bar top.
You should be able to find some crown molding at a Home Depot or a Menards that will do the trick. I’m not sure, but I think they might do the cut for you on an uncut piece of crown molding for you for a small fee. If not, Try a more local lumber yard that does custom stuff. It shouldn’t be too expensive (well, less expensive then buying a table saw.