Tidy enclosure and fibre controls
Mark VIII introduced the control unit first intended for Mark VII. A fibre optic cable to replace the string-and-switch charge control, and in future the discharge and safety relays. With the new controls it was also almost possible to enclose the charge unit entirely in it's own box, both safer and tidier. Almost, but not quite - a few more changes are needed to remove the need for a bulky external supply for the charge isolator relays.
The first session of the MK VIII tested it upon three victims: A pineapple, a tomato, and a can.
Three weeks later, the Mark VIIIa alters corrects the flawed power supply for the charge isolation relays, allowing the charger to be completly enclosed in safe, insulating plastic.