You don't mention the tank. If it is the 2521 tank w/ 1 6-sheet reel then it only needs 270 ml of developer.
Jobo tanks are made to be used horizontally. If you don't have a Jobo processor then you can either roll the tank back and forth on the the table or use a motor base. However, a 2521 tank is too short for comfortable use on a motor base -- two fixes are: attach another tank to the bottom of the 2521 using the magnets on both bases; or slide the tank into a longer length of PVC drain pipe, the tank can roll around inside the larger pipe so it doesn't need to be any sort of tight fit.
If you are only doing 2 sheets then use a 4x5 or 5x7 tray.