Set off a DFC today, and it broke through GT6 bedrock ores at Y=0. It would be nice to have a config files that allows the user to specify blocks that should be immune to explosions.

You set off a DFC, potentially the most powerful explosion in the mod, what were you expecting? Of course it's going to rip through everything, that's the whole point.

I'd rather not have holes in the world floor.

Then don't use Schrabidic nukes or set off DFCs.

I mean you kinda signed up for the "holes in the world" part when you decided to start up the DFC, the gap in the last bedrock layer adds a bit of spice to that.