Storm32 Gimbal positioning issues

I’ve been pouring over all my settings and just can’t figure this out. I have a 3rd joystick connected to my transmitter on ch9/10, for the purpose of controlling the angle of my gimbal. I can use these channels to move the gimbal, but as soon as I release it, the gimbal returns to center. Is there a way I can have the joystick affect the relative position of the gimbal, kind of like flying a quad in acro mode? When the stick returns to center, the craft simply holds that angle.

Here are my configuration settings

Also of note, I cannot get the gimbal to function properly using protocol 8, per , when I enable that (and disable the heartbeat on the Storm32), the gimbal just starts spinning around after powerup.