What kind of process has 8 minutes of dead time? I once worked with a plastic extruder with about 5 minutes DT.
About the only thing that seems to work is either a plain PI with a gain of much less than one and very low reset rate, or a Smith predictor.
The Smith predictor will allow the use of a higher gain, and therefore better disturbance rejection. However, it won't overcome the dead time as far as setpoint response and rejection of some types of disturbances.
I think that the only thing that will really help is a crystal ball.
