hmmm sausages, Carl
Seeing your concerns here I decided to make some black puddings using my latest batch from sausagemaking.org. My findings, for what they are worth, is that the mix does come up a fair bit wetter than previously. With your experiences in mind I held back on the water on the first batch, which I stuffed into ox runners. This resulted in puddings which were very firm as you can see in the picture. I also had a split which has not happened before using runners. I assume that it absorbs and expands during cooking. The second batch was made using a bit less water than the recommended recipe at 1.5 kg. This resulted in a better pudding albeit a wetter mix. Your observations regarding the fat floating are correct, but once the casings are filled and cooking ensues, the fat seems to distribute well... as can be seen in the picture. I left both batches to soak for about 40 mins. The first batch I was still able to stuff using my little stuffer, but as the second batch was more liquid, and the casing larger, I opted to fill using a jug. It looks in the pic like the puddings are different colours but it is down to the camera flash.
In future I will stick with the recipe and expect it to mix wetter. Just thought it a bit strange the texture of the mix was different to what I had used before.
Hope this helps, and allays any fears.
Regards, Paul Kribs