I just developed my first 8x10 negatives in a Jobo Expert Drum this past weekend. (Though I tried tray processing 8x10 first) After reading and looking at the various information, I settled on 200ml per sheet. For 5 pieces of film I used 1 liter of fluid in the expert drum. The results look pretty good. I also have Unicolor tanks here, and know you can only put one 8x10 sheet in it at a time. I would suggest at least 300ml of developer, that should be more than enough to insure good development.
I agree with the post who said take two of everything, I took two shots of everything. Next I am going to try identical shots, developed in Pyrocat HD and see what the differences versus my usual D76 and Rodinal.
Gary