My current Mammoth hauler is now back to where my old one used to be, before I lost it: Able to haul a full jettisoned container (Jet Can) worth of ore.
27,668.4 cubic meters of ore, to be exact.
The Mammoth actually holds 21,368 cubic meters, but by placing seven Giant Secure Containers in the cargohold, those magic 3,000 cubic meter boxes that hold 3,900 cubic meters of stuff, I managed to get to Jet Can size.
That is still a bit shy of the 29,890 cubic meters of ore my old Mammoth could haul, but still respectable.
I got back to Jet Can strength hauling via a two pronged approach. First was the old stand by, the Cargohold Optimization I rig.
It takes 100 Alloyed Tritanium bars to make one of those, along with some other, less expensive salvaged material. And if you salvage actively, you know how rare they can be.
After months of salvaging, I managed to squirrel away 70 of them. I bit the bullet and spent about 12 million ISK on the remaining 30 I needed and made the rig.
That got me up to 20,513 cubic meters, enough for six Giant Secure Containers, but just shy of the seventh.
Not quite willing to part with another 45 million ISK for a second rig, I decided I could use my vacation to get that 7th container in the bay.
I had already trained the skill Minmatar Industrial up to level 4. Each level you train gives you a 5% cargohold capacity bonus. Getting to level 5 would put me over the magic number.
So before I went on vacation, I set my skill training to Minmatar Industrial 5. A ten day skill that could run during my time away from home.
And now that I am back, my hauler is set.
I just have to find the time and energy to do some mining I am, frankly, still beat after our vacation!