Well before I commit to this problem I want to know how you came to be in a "wet paper bag".
CWI won't help, they'll just want to critique the job after its done.
Sounds to me like this a high pressure application so take your pick of codes ASME or API, if your in the USA.
6G
Brazen it out might be good advice; use a high silicon bronze filler... alternatively, a multi-pass face deposit of any convenient alloy might be deposited, ground to as nearly perfectly flat surface as practical, and polished to a mirror shine. By looking into the reflective surface you can see what you saw, extract the saw and cut your way out.
...think you got it tough, how'd you like to have been in Taiwan when that sperm whale exploded?
"The 56-foot long sperm whale was being transported through city streets on the truck after it was found beached during the weekend. It was being hauled to a university where scientists were going to try to find out how it died.
Right in the middle of traffic, the carcass exploded - splattering its innards across the street.
Experts believe the explosion happened probably because of gases building up in the dead mammal's collapsed stomach.
Shopkeepers closed up so they could scrub away the malodorous mess of blood, blubber and entrails" (from CompuServe News report).
Now thats a bag of um!