I measured the Mammoth @11.75", if memory serves me correctly, it wouldn't be a half inch clearance... you'd need a different box.
Even @15L load, I'd get a lot out in a few hrs every day!
Tandem & tri pup should do pretty well (maybe close to 10L) if the corners aren't too much trouble to navigate.
Your series of Mack, did they ever make 6wd? That makes a huge difference for steering control, especially when carrying alot weight on the front axle.
I have 3 Stahl models & now the 850 with a 4.8v rx battery installed with the BEC coming from the Sabertooth esc as well. I never have to recharge that rx batt b/c the BEC from esc is keeping it charged & the batt takes care of the current spikes when they happen so no glitches or time outs.
Here's some pics of tires... I did some horse trading with PFB, got his excavator dollies, so I think they're the same tires you're using? 1st pic - tires from the wheel loader & the other is from the adt.
Nathan used that foam wrap to fill the tires, which created a flat spot where ever it ended... I tried to redo it, butting the ends together with each wrap, but still had a bit of a flat spot where it met. I tried a few other tires I have on hand, but they don't fit the Mil-Spec rims.,..
Then it occured to me today (while taking the pics) that I should turn out some tire fillers from oak!
Make the donuts, cut each one in half so I can get them inside the tires for a true round smooth rolling tire... then maybe I can use them without pulling the track hoe out of the dollies b/c of skidding wheels while on the move?!