yeah I thought Vy would be THE speed for skydive ops.
Although I think I've found the answer:
Basically if the POH says Vy is 107KIAS at maximum continuous power (say 675hp) then any setting less than this will decrease Vy. Suspect these operators are running their -114's at a reduced power setting.
thanks to:
http://www.pprune.org/tech-log/343259-vx-vy.html
What is Vz? Are you referring to Carson Speed?
I don't see any reason not to believe a POH that states Vy = xxxKIAS. Why would they make that up? Surely it was determined with data.