Camera Gimbal control with Taranis X9d

Any suggestions for controlling a camera gimbal with a Taranis X9D? Its on a octocopter and I just worked out that all the other channels are on/off button type. So nothing left to control my sliders or pots?With a Frsky X8R it works fine but am hopping to run on OpenHD only.
Taranis X9D OpenHD 2.0.8 running through Mavlink 2