Jim:
Just a quick warning, be *VERY* mindful of where you attach the chain to the tractor, many have been killed by a tractor flipping due to inadequate care!
The problem is simple: if the log/thing being dragged gets caught on something solid (i.e. a stump, rock, etc.) then the chain attachment point forms a lever that works to rotate the tractor about the rear axle.
If you are using the drawbar, and the ground is fairly level, then the lever is short and below the axis of rotation - working to keep the front wheels down.
But if the attachment point is effectively above the axle (which can happen even if just using the lower links - if they're raised some) then this force is working to lift the front wheels off the ground.
If the tires grip while this is happening, LOOK OUT! /forums/images/graemlins/shocked.gif It only takes a quarter of a rotation for it to be unstoppable...
The safest method is to use the drawbar, ROPs and seat belt, and be very cautious - expecting the worst.
Good luck and stay safe.
Bruce.