Had a Chevy 3500HD SRW pass me locally yesterday and saw something kinda odd on it's susp. Attached to the rear spring shackle and axle itself was a some kind of coil over shock (at least that what ...
Installing any coil over shock and expecting it to assume an overload condition is asking for trouble. Shock mounts, in general, are not beefy enough to carry weight. Shock mounts are built to carry a shock and absorb the shock stress, not carry a load all the time.
It's a cheap out way to increase load capacity while stressing something that isn't designed or built to carry a sustained load.