Just to finish off the discussion of the manufacturer's intent regarding "mismatched" components...
I sent DuraSafe this question:
I see on your website that the Trailer Guardian is intended help "prevent accidental decoupling caused by mismatched ball and coupler..." By this, do you mean accidentally losing the trailer because it has a different size coupler (2", for instance) than the ball on the hitch (1-7/8", for instance)?
and they provided this reply:
Thanks for contacting us. Yes, the Trailer Guardian does prevent the coupler from accidentally popping off the tow ball during travel if an improper tow ball size is used. There are instances when people either forget or don't realize a coupler calls for a specific size tow ball and when not matched up correctly the coupler can pop off. This can be a dangerous situation.
I would still rather ensure that the coupling is correct by the methods recommended here (pulling up with the trailer jack) than hook up another device each time; I would rather ensure that the ball is correctly installed (such as by the methods Pete described) than install another device; and the think the "pre-flight checklist" approach is more valuable than adding another task to be forgotten.
But hey, if it helps you, go for it!