extra thought, horizontal drill, once drilling indentations,

from the top, instead becoming angular, as in    \

go straight perpendicular, as in   |

and eat away at the protruding portions.

Indentations mean, far less strain, easier deduction to the mass.

Angular would be slower, but that will also create less strain as it is not fighting as much as the perpendicular angle straight down....

Anyway, whichever is more advantageous.

Who am I talking to I have no idea.

Trustworthy people later on I guess.