Finally found time to look into this. For faster trim control, you should really be using offset 0x0BC0 as described in this post: https://forum.simflight.com/topic/90988-installing-and-registering-fsuipc7-and-widefs7/
I tested in the C208 and this works as expected, although I found an increment/decrement of around 500 to work well for me.
Note that this offset is currently (incorrectly) documented as not working for write access via the sim variable (ELEVETOR TRIM PCT), but it is working but using the key event ELEVATOR_TRIM_SET.
I will update this.
If anyone has any further issues when trying this, please use the FSUIPC7 support forum, and please specify the aircraft that you are using.
John / FSUIPC