The cycle looks flat to me.
With Kitty, anything less than .5 units had no effect on her. BUT, some cats are very sensitive to insulin. The .2 difference could be "a lot" for diablo. It is hard to judge a dose on one cycle, but if I was judging this cycle I would say .6 was not enough.
Just my thoughts..
Sometimes you can tell more if you stick with a dose for a few cycles.
Good Luck