The additional length I worked out like this:
CO 70 sts
knit 3kx2p ribbing for 3”
decrease 1 st every round for 5 rounds(65sts)
knit 3kx2p ribbing for 2”
decrease 1 st every round for 5 rounds(60sts)
knit 3kx2p ribbing for 1”
decrease 1 st every round for 5 rounds(55sts)
knit 3kx2p ribbing for 5”
continue original pattern from thumb to finish.
The decreases (which you can do every other round if you like but be mindful of length) I placed all along the same line as the thumb.

This is for a friend out west. It has been a wonder watching the Cherry Tree Hill and the Louet transform into this lovely rich fuzzy stuff that looks so different from it’s sources.