i have proof of wanting to try your best, to pull your arms in and across your chest. when you start rolling the G forces, alone can be enough to really tug on you. to pull your hands and arms out and away from you.
my right hand was crushed, been way to long ago to remember how many broken and crushed bones i had in my hand.
driving 4 wheeler, that ya sat down into, with a roll cage, going little to fast, and turned a little to quickly, and rolled it, my hand flew off steering wheel, and out between roll cage and ground.
seat belt should be adjusted to you, and on. it is normally not that hard to adjust most tractor seat belts.
the roll bar / ROPS. stands tall so when it does flip over, your head and body stay in a good zone. ya you might get a couple scratchs on face from a weed, but that is about it. or less you roll over some logs / large bumps that could protrude into the safe zone of what the roll cage protects, then it is a different story. and no putting your hands and arms around your head or body will protect you. best you can do is try to keep your feet, legs, arms, hands inside the safe zone. and let the ROPs do its thing for you.
again keeping your hands and feet inside the safe zone can be problematic. once you start rolling G forces alone, to no longer seating in seat but hanging from seat belt. can make it difficult to keep things in the safe zone.