I used a pure bus grounding scheme. You can see the ground bus running along the edge of the turret board near the controls. The output stage is to the left, and the input is to the right. The ground bus connects to the chassis only at the input jack, which is not insulated from the chassis. This grounding scheme worked out great. There is no audible hum or buzz in this amp.
Some people recommend connecting the chassis to the first filter capacitor, and insulating the input jack from the chassis. But I think a better case can be made for connecting the chassis ground at the input jack. It has worked out well for me in several amps. It is also the scheme recommended by the old RCA tube manuals.