I still am not sure why the kegs were despawning, but we changed to timer to 50 minutes and with only a few hours of time left we picked up the pace and got up to 47 kegs, recounting when we loaded them into the rowboat.
halfway through attempt 10 when we should of had 72 kegs (moving those kegs out of and back into the crows nest every hour and a half to make absolutely certain we moved them all in time) we recounted and found we only had 29.
On a whim we counted them when we went to load them into the rowboat and found we only had 16 kegs. And we learned that the 2-hour island loot despawn timer applies to the crows nest.
We didn't discover the issue until attempt 9, our target had slowly been creeping higher and higher when on this try we had stacked 83 kegs. up to this point we had been adding the kegs to the tally when we put them on the boat/ in the crows nest.
Honestly, we thought it would be 1, maybe 2 sessions for a funny stunt. But in our initial attempts we were met with either blowing up in the process of stacking or the Redmaw not dying despite us having more than 35 kegs.
We then decided our target would be a Redmaw to avoid potential confusion with the Barnacled Dread's armor (we weren't sure how the separate health pools might affect our numbers)
As for the damage numbers we started by killing a skeleton lord with the kegs to get a rough idea of the damage per keg, and estimated it was between 325-350 damage per keg. From past experiences we found it takes ~100 cannonballs to kill an ancient meg, so our target was between 30-35 kegs.
For anyone curious about the details/technical aspects: We used 47 black powder barrels, 1 regular keg, and 1 keg from the rowboat. We chose a cannon rowboat because unlike other rowboats PvE such as megs will aggro onto it which allowed us to detonate the kegs when the meg charged for max damage
"They fear the shadows, but I embrace it's shroud, it's whispers. One step closer and it will cover you not in it's soft embrace, but a prison on insanity, fear, and thorns"
"Oh there's nothing quite like my Yarrrrley-Davidson. She's a 1985 model with a 40 Horn-of-Fair-Winds powered engine who can go from 0 to 60 knots in 12 seconds, Wanna ride?"
Bounties were given to many crews for her skull, but only few returned, none victorious. They say she claims a prize from every attempt, sail cloth, ropes, clothing shredded by her However, if you have nothing she likes, your soul becomes another serpent in her hair
With gilded talons I shall order all who do not bend the knee to Captain Flameheart be cut down and their vessels shall made nothing but driftwood, an example of what happens to those who try to be heroes