Sh7eleven,
I moved the ground buss that connects B9 to 10L. Then there is room for all the drain wires, but just barely. It helps to have the weaved bus wire that threads through 8L parallel to the chassis and not bent down. If it is left straight, All the drain wires fit. Then after you solder 8L, you can bend the bus wire down out of the way. I have only built two Stereomours, but I believe that terminal 8 is the center of the star connected ground for the circuits. The safety grounds are all at the back of the chassis. You will note that after attaching the C4S board, the ground comes up from 10U to the C4S board and then over to PS board. I don't think running the driver tube ground to 10L hurts anything. There is no current flowing through pin B9 anyway, it only sets the ground reference for the heater wire of the driver tube, acting as a center tap on the heater windings. Here is my build at that point. I used a continuous bus wire starting at B9 to 10L then 8L and finally 6L. I left insulation between B9 and 10L.