I ran a roll of the HP5 through the Mamiya Press this morning and developed it as recommended about, at 7.5 minutes. I also was unsure about the fixer but did it for about 7 minutes and the results seem okay. But I must confess, people keep saying that you learn the fine points of developing through trial and error etc., but at this point I have no idea if things I see in the final product are a result of the film, my technique, the camera and lens, or the developing. I don't even know where to begin, but so far I have been pleased with the results.
First roll of 120 to home develop!
The area where I feel most inadequate is just basic photographic skills when it comes to black and white. I still don't have the eye to be able to spot scenes and lighting situations with the naked eye and imagine how they will look in B&W. My hunch is that lighting is even more important in B&W than color, simply because that is more or less the only variable. Anyway, I keep trying!