The plate which shipped with my Sirui ballhead included a large QR plate
which I don't intend to use, while the others I bought are smaller.
The difference is the plate undersides: The original is free of hardware
other than the screw for camera/lens, with the others having two
hex-head screws each:
As these plates cannot mate to the head in any way with the screws installed,
I am quite curious as to just what these screws are for, because the heads
protrude below the bottom of the plate with no room in the head's socket
to accommodate them.
I therefore ask you knowledgeable folks here what the purpose of these may be -- ?
I'm at a loss in understanding it, other than to imagine mounting to accessory devices
such as gimbals or somesuch...