Have read several extensive threads on cranks and weights on OGF.Seams that its difficult to get a concensus on how deep the crank is going due to so many variables.Then you take into account of where you put the weight on the line too.Last season was the first time I even tried putting a 2oz weight 50ft behind crank and putting out to 150-180 total line.Some days they caught pretty good,but using it for first time was worried about using two boards per side due to possible tangles.
I agree with Juls,when it comes to trying to figure out depth of these cranks.You are probably in a range of depth you want lure.Have several at different depths,see what catches and reproduce that lead.
Have also read that another factor that catches fish with cranks is the vertical movement of crank in water as it moves up or down with changes in speed.That is a factor when making S turns or 180 turns.Or speeding up or slowing down.Fish will strike lure as it rises in water.