The purpose of the test (and my original question which lead to it) was an attempt to get the best out of what I have. I recently changed to HP5+ from FP4+ for the reasons I gave previously. I had also used Rodinal/Adox Adonol for many years and had just purchased a new 500ml bottle, so was looking to capitalise on my investment.
I am fully aware that there are other more capable developers, but I (and a small band of sad people here ) like Rodinal and the results it gives.
Like the engine in your favorite old car/motorbike/lawnmower/boat, it's a worthwhile and rewarding experience tuning to get the best from it. You will of course get a few who will say, "why not just by a new car/motorbike/lawnmower/boat".