So, with the coarse mill I made a prefement, based on a millet starter. The red rice hydrated and fermented quite well. When I made the dough I included some of the fine red rice flour, as well as some very fine red sorghum flour.
The result was quite satisfactory. good oven spring. Unfortunately I got distracted and left it in the oven a little long - but that provided a really crunchy crust!
The crumb has a grainy texture from the cracked grains of rice, but as it was well hydrated, it is smooth and easy on the palate. The fine flours brought it all together into quite a pleasant bread. Flavour is interesting - it is reminiscent of Russian Caravan tea, with light, earthy smoky overtones. Quite a satisfactory and unique gluten free sourdough.