Hi Kathy!
I don't really know why sometimes the shave will work after decreasing due to an inverted curve and sometimes it doesn't.
I have noticed that the inverted curve can happen when Pepper is not feeling well too(allergies, constipation, etc).
However, our flat green kitties will sometimes show us that they are ready for a dosecrease by the inverted curve. I like to call it Pepper's upside down rebound.. lol!
I found this quote in wikipedia regarding rebound: If the rise after peak action is faster and rises higher than the original pre-insulin level and the original fall in blood sugar, you have good cause to consider rebound. The only sure way to check is to reduce dosage and check for a better shaped curve.
I have to admit that I sometimes wait for the green.. as Pepper has a hard time holding dose (he's been here awhile..).
However, since Kitty is feeling good and continues the inverted curve.. reducing a shave couldn't hurt and if bg levels start to creep up go right back to the original dose.. Kitty is farely new to diabetes so he may react real well to the shaves! Soooo sneaky!