Okay--here's the report.
This milk followed the same low starting pH trend as my last few makes in the Spring--the pH when I reached temperature to add the culture was already 6.45. I'm going to do some experimenting with different sources of milk to see what I can learn.
I learned a number of things from working with twice as much milk as I was used to. First, in many respects it was exactly the same as working with only 4 gallons. The real differences, for me, came when it was time to drain. I had a harder time getting the curds pushed to one side of the vat so I could pull the plug. Later, when I put the curds in the molds, I learned that it takes a lot longer to put curds in 9 little molds than in 1 mold (I knew it would take more time, but I was surprised by how much more time it took). I don't have any pictures of all of this because I was little frustrated during that process.
Once I got all the curd in molds, I stacked them and began pressing them.
I learned some useful things here, too. My new, big press, isn't invited in the house. I had to press the cheeses in the garage.... I also learned that my cool stack holders aren't that great and that the press as it currently is, is not stable. While making adjustments to the threaded rod on the press, one of the towers broke and shot my little cheeses all over the place. Luckily they all stayed within the molds, so I didn't have to throw them away. I scrambled trying to figure out how to press all 9 cheeses at the same time. In this process I learned that trying to press cheeses in parallel, like the picture below, really requires that the molds are filled as close to equally as possible.
I also learned that my garage looks even more messy from the angle my kids see at.
After pressing for a while, I checked on the cheeses and was disappointed to see that the rinds were not sealing up very well. I increased the pressure and let them press longer, but it didn't do much. I decided to try something I had read about and dropped 6 of the 9 into 160 F water for about 3 minutes and then pressed again. That helped, but mostly led to more extrusion.
I'm not sure if I should wait to cut off all the flashing (the thin extruded stuff) when they are drier or do it sooner.
In the end, they all turned out okay, not perfect, but good enough for today. With all the things I've learned, I'm really not too disappointed. I will let them dry a little now and will then continue the experiment with the different rind treatments.