How to create deeper RWG maps?

[Brashnack]

Quick question:  How do i edit the config files to make bedrock deeper than it normally is?  Right now, the map I've generated to play on is only about 35m from bedrock where i want to make my base and I'd like it to be more like 50-100m (i like to dig a lot).  I've only generated the map and scouted it out, so i haven't begun playing on it and can regenerate it without losing any progress.  Thanks in advance for any assistance.