My APC Petit Standards have a 16cm leg opening. They're a size 25 and fit similarly to DH 17.5cm in 27. I don't find the leg opening to be too small but I have tiny calves though so take that with a grain of salt.
Finally saw it yesterday. Worth the wait seeing it in IMAX in Lincoln Square, sitting dead center with less than 20 other patrons in the theater. Also helped that I went by myself. Although Caine had very little screentime, every time he talked I wanted to cry