Bob, I just sent you a reply, but let me know if you have any other questions.
Thank you, and thanks, Alan.
For those interested in knowing, I wouldn't recommend the PRP-55 for large format.
It can handle the weight, but because the contact area between QR plate and camera is small, there won't be enough dampening, and the large camera will wobble.
The PRP-55 would be a good choice for DSLR or medium-format systems; it's small, lightweight, and reliable.
For an 8x10 camera, the smallest ball head I'd recommend is a CB-48 size, and a QR set that matches well is the QRP-70, or the SRB-60 clamp with 70mm plate.