FSX requires FSUIPC v4. However, there were issues with FSFlyingSchool's interpretation of vertical speed with early versions of FSUIPC 4. It's working just fine in the latest version of FSUIPC 4. (4.07 at the time of writing).
If your system is running fine - don't change anything!
If you suspect FSFlyingSchool is giving incorrect readings from FSX, please download and install FSUIPC v4.07 from here:http://www.schiratti.com/FSUIPC4.zip?timestamp=260107