To me it's not a "personal decision" -- there are other people in the payload section of this overloaded situation. Taking the risk of turning your tractor over on yourself is one thing, but doing so with 20 folks in tow is a different matter.Look again. No ROPS upon which to affix the card suggested. Each guy gotta do what he's comfortable doing, I guess. It's a personal decision, so I'll back out of here now.
I don't have a BX24/25 manual but the manual for the (comparable size/weight/power) BX2360 shows maximum rated towing capacity of about 1700 pounds. Let's assume Kubota built in a factor of safety of two; that's 3400 pounds. The OP states a 6000 pounds tow weight situation, and that is more than three and a half times the rated towing capacity of the tractor.
As for "well nothing bad hasn't happened in the past so it must be safe" -- that type of false confidence is a recipe for disaster. Read Feynman's contributions to the investigation of the Challenger shuttle accident for reference.
Rogers Commission Report - Wikipedia, the free encyclopedia
Like I said, it's one thing to take risks when you are the only one who may get injured/killed, it's another to play ferry boat for customers with a ship too small for the load.
Wrooster