Okay... Call me crazy, but the plaster just flew off.... This was a small (too small) bit on an air hammer... My guess is with a 3"or 4" spade bit would make the work go easy for the most part. Still not fully ready to take that leap...
This is a chip-out around the CareTaker... Its about an inch to the gunite... Little bit made fast-fast work of this area....
[click image to view] And then this is a poor video of the limited work on the wall - I only wanted to see how hard/firm the plaster was...

This is a chip-out around the CareTaker... Its about an inch to the gunite... Little bit made fast-fast work of this area....

[click image to view] And then this is a poor video of the limited work on the wall - I only wanted to see how hard/firm the plaster was...
