I thought the following might be of value to others doing upholstery work on their cars.
I have been working on installing the headliner on my 57. I found that my air stapler was blowing the staple thru the headliner fabric, running at 65psi (a pressure that had worked well when I was previously working on windlace installation). I kept backing off the air pressure, until I found I the staples didn't blow thru, which was at around 35psi. After a while, I then found that the blade that drives the staples wasn't fully retracting into the tool, so the staples couldn't slide under the blade, and be driven. I thought there was something wrong with the stapler; when I called the customer support number, the tech said I needed at least 45psi to properly cycle the stapler. That would put me back to blowing the staples thru the fabric. He told me some people stapling fabric had success by grinding a bit off of the end of the blade that drives the staples. I took off about 1/16", and then a tad more. The stapler now cycles properly (@45psi), and doesn't blow the staple thru the fabric.
Regards, Doug