Imho placing a minehole without rustroot isn't a waste. You'r going to look for metals that are deeper anyways, and you need to go down L2 to look for metals at L3. And it's extremely easy to avoid cave-ins when you understand how it works and it's as efective as zig-zag i think.
Op wrote:Thanks. Has anyone placed a mining hole yet? If so, do bats spawn in them?
They do spawn in the minehole caves. I have only noticed them in the areas that I have mined out though. Not in the 9x9 area the minehole creates although this also may happen.