Sorry for not being more clear.
I did connect the the signal grounds to the chassis.
To expound on the subject, I used XLR balanced signal input jacks on the back panel,
the signal grounds from them were hooked directly to the chassis using short (<2 inch) wires
soldered to a header strip that is bolted to the rear of the chassis. The board grounds are also soldered to
the same header strip (through 1K resistors) in a centralized "star ground" configuration.
FWIW, I believe that multiple ground attachment points to the chassis should be avoided.
That would be inviting possible noise pick up into the system.
One other minor detail, if your chassis is anodized or painted, abraid the ground contact point
for the fastener to ensure a good connection directly to the bare metal.
I also use star washers to give the physical connection "a good bite".
Lastly, I use a nylok aircraft type nut to keep things from ever coming loose. A solid ground connection is what you want.