I just installed a brand new driveshaft on my modified snowblower. Chain from tractor end of driveshaft cover to chain connection on blower end of cover. Chain from blower end of cover to connection on the blower frame. Two benefits: You don't have to clip/unclip the tractor end when connecting/disconnecting the driveshaft from the tractor, and the chain between the two ends of the cover prevents the driveshaft coming apart if you were to extend it too far. I cut both chains to be just the right length. The chain between the two ends is just long enough to allow for full extension with highest 3 point lift. With [lower] running position, it allows the front half to wrap about a third the way around the driveshaft relative to the back half.
I tested it today, and works like a charm, raising and lowering while running worked fine. I expect if the interconnecting chain were loose so as to allow a full turn wrap around the driveshaft, that would not be so good...