I'd say more of both couldn't hurt, but definitely some rocks with flatter surfaces. All of my Thorichthys also seemed to favor any any cave-like structure. Does not necessarily have to be an actual cave, could be a rock with some overhanging driftwood etc.
As for a larger group, what is your current m/f ratio? I started with 10 T. pasiones and ended up with a group of 5 as something slowly killed off the others. Still not sure what it was, but they would slowly just waste away. All the other fish in the tank were completely unaffected. The remaining 5 only left me with a single male, and from that he would entertain 2 different females sporadically. They'd defend an area, go through the motions of head-shaking, cleaning a rock, etc. but never actually spawn. Not sure what exactly the issue was but I just recently sold off the group, hoping it would spark my C. robertsoni to spawn with their "competition" removed. Well, I have 6m/2f C. robertsoni and one definite pair. They guard a spot pretty aggressively, constantly are cleaning and head-shaking, yet again... no eggs. So, I am at a loss. I'm on the verge of placing some clay pot saucers in the tank, under the assumption they simply don't feel as if the many rocks within the tank are adequate enough, yet I've seen cichlids spawn on much stranger/less ideal surfaces.