Hey guys, I have a problem with my structure spawn. Problem is it spawns way too high and way too frequently, here's what I mean:

 

 

 

 

Since it's a cave I want the bottom 4 layers of the structure to be below the surface Y

 

but I don't know how to do this.

 

Also, I'd like the structure to not spawn as often as this, any ideas?

 

 

Code

 

Here's my WorldGen class: http://pastebin.com/rCU7vbBP

 

Sharing the face cave code is a little long and tedious, but here's some of it (it's over 3000 lines long): http://pastebin.com/rKEWncc6

 

Nobody?