I genned a world with the full 3 cave layers but each layer as close to each other or the surface as possible. I've tunneled down more than 50 layers beneath the surface now before breaking into a cave layer, and this cave layer also marks the first metal I've found despite one of my biomes having been listed as 'shallow metal' alongside 'deep metal.'
I only get about 50 FPS generally, so it was an investment of a few hours to even just discover that this embark was absolutely trash for me. I like that metals are scarcer, but I feel like the degree of the scarcity could still use some fine-tuning. :F
The worst part about this, too, is that I add ENVIRONMENT:SEDIMENTARY:VEIN:100 to native copper (and METAMORPHIC for malachite), and add small clusters of cassiterite to more types as well, but I still found absolutely nothing prior to the galena 52 z-levels below the surface!
At present, it just feels like -- if this pattern holds, needing to breach the underground to find any metal -- that the game is sort of
forcing my hand to make the fortress
at the underground. I used a Play Now! embark this time, but I think from now on I'm going to need to add copper to my preparations so that it's more feasible to just tunnel down and begin the game at the underground ... this really makes me wish alluvial small clusters and stuff that's seemed to be broken for a while was more functional, though, because putting more emphasis on digging deeper makes those would-be tracer deposits so-much-more-relevant than they previously would have been.