I don't know if this was intentional. I hope not. To apply Travertine Keys and Radiant Sources one needs an optimum ability of 1425. As far as I can tell, no biped can reach this level without benefit of a workshop and the lava tube is definitely not a workshop. I don't believe bipeds can get above 1390, if that. Therefore, we are 3:1 applying those units to the lava tube. It's very hard already, but having to make all those extras on those two resources doesn't seem right.
Love, Cixi