You got me interested in basalt. Started reading some. My latest boards ditched the balsa rails, too much work and cost. I've been painting them black. One thing I don't like about that is when you get an impact, the cloth "snackles" and the white fibers show up in a glaring way. I was thinking the basalt cloth would look nice on the rail with the wood and would be a good strength addition under the deck veneer.