Over the past 5 years or so I've experimented with various patch set configurations to determine what sets worked best with my 3 printers, 9500 II, Pro1000, and Epson9800. I used an i1isis 2 XL with page US letter 8.5x11" pages.
I've found a few printer anomalies. The 9500II patch color shifts a bit depending on the patches printed to either side. For instance a dark color tends to become darker/more saturated if the adjacent patches were similar. The Pro1000 tends to print differently on the first page than subsequent pages if it hasn't printed in a while. The biggest differences are after a time delay of a week but there are significant differences even after a few hours. The 9800 was the most stable but showed gradual shifts as the cartridges aged and ink levels decreased over a year. Likely due to gradual evaporation and ink density increase through the breather tubes. Still, remarkably stable. Even though the 9800 was most stable, the profiles needed to be somewhat larger for similar accuracy due to the printer's more lumpy RGB response. Especially on the neutral axis.
However, by creating a tool that combined patch sets, randomized them, and added extra patches to each page to detect page to page printer changes I was able to get good, consistent results and came up with quite good patch sets.
For smaller size patch sets (<1500 or so), embedding an inner grid produced much better profiles. As an example, an inner grid 4x4x4 inside an outter (main) grid of (5x5x5) produces 189 total patches and a side benefit is that the spacing between neutrals (R=G=B) is halved.
However, the advantage this has decreases gradually and at over about 1500 total patches disappears and the conventional, single grid performs as well or even better for larger patch counts.
For each of these approaches I also found a large improvement in neutral and near neutral color accuracy by adding a series of near neutrals RGB values. The main reason is that DeltaE 2000 is much more sensitive to small colors changes along the neutrals so extra patches significantly improves prints that have large areas of low/no saturation color.
I made large set of the RGB patches, both with inner grid and only the standard grid but all with extra near neutrals. The ones with the inner grid are labeled optN.txt where N is the total patch count and linN.txt for patches that only use the standard, outer grid. Also, scrambled versions are also provided. They have the exact same RGB patches but are randomized to reduce regional color shifts such as occur on my 9500II. These have a file name ending in 'x'. I prefer the scrambled but the unscrambled ones are easier to visually identify gross print errors such as selecting the wrong paper type.
Attached is a zip file containing these.
