For what its worth
I've been using a small Del's Merkin for bonefish for the past two years with more and more success. I don't use them up here except as a novelty. I've found that if you can get a bonefish to see it ON THE BOTTOM they will eat it. My method with it includes hoping the fish sees it either on the drop or swim within a foot or 2 of it when moving along. When this happens. I will move the fly 2-4 inches, no more- the lesserer the betterer. At this point the fish swims over the fly and stops they now have it in their mouth,every time so far.
Over Thanksgiving I was in the Bahamas. I was messing around at lunch and found some dime sizes tan crabs. When I approached these crabs they would run along the bottom and stop when they got to any kind of structure (including a piece of broken coral the size of a quarter. I saw numerous crabs do this same behavior. None of them "dug in." Simply stopping makes a lot of sense as digging makes noise and includes movement alerting both visual and auditory senses. Also, when these crabs stop they blend in and blend in well. for all those who think not much "noise" could be created by digging think that those tiny rattles people put in theit flies make noise and a palmered hackle supposedly makes noise going through the water.
Some of this stuff may seem a bit out there but it seems to be working.
On a totally different tact I met a guy who used to cast one into the wash on Nantucket when mole crabs were present and just let it basically wash up and down the breaking wave area. He said he caught a lot stripers that way.