Worth mentioning here I thought as many use the popular NX6 or NX8 transmitters.
The latest Firmware update (version 4.xx) from a few days ago upgrades for free from 6 (NX6) to 14 channels and from 8 (NX8) to 20 channels. Which means you can use all switches you have for options in the Spirit controllers. Even an 8 channel (AR6610-T) receiver outputs 20 channels over SRLX2 to the Spririt. All 10 switches can be used in the settings. Tried it, worked.
Finally I can be using many useful modes for which earlier I didn't have channels for (but enough swithes on the controller).