The whole topic is pretty entertaining to me. Lifting a 100 lb bucket 3 feet off the deck does not raise the center of gravity of a 5000 lb tractor by a substantial amount. The wind resistance is negligible unless you are on a race track or near a tornado compared to the weight of the tractor. You could just park it on the trailer and not have a problem IF you drive appropriate for that set up (slow enough). On the other hand, you could strap it down with with 10 chains, and lower your ROPS to decrease center or gravity, heck tie it down too but IF you drive like an idiot you'll still have a problem.
In other words, the way you drive makes a much bigger difference in safety than how you set it on the trailer. Having an appropriate tow vehicle/trailer set up makes a much bigger difference in safety. Being sober and not talking on your cell phone while driving makes a much bigger difference in safety.
I once used the dump trailer to move my tractor instead of using my deck trailer. The sides were 4 1/2 feet high, and the dump trailer not long enough to contain the tractor and loader and get the right weigh placement, so I rested the loader arms on the trailer lip with the bucket hanging over the front. Should I do penance? Can I buy an indulgence?
It has been my experience that if I "think" I should have secured something better it usually follows Murphy's Law. Therefore when it comes to loader, mower, etc. it is grounded and secured with an extra chain or two just to make sure, lol.