Each boat setup could vary. Best thing to do is find a flat without snags (preferably) and cast your jigs out and begin trolling .8 mph towards shallower water. Watch your poles until you see them bouncing and look at your finder. This will tell you what depth they begin hitting the bottom. I would also recommend you do this little study with all you intend on pulling (1/32nds, double 1/16ths, 1/8ths. etc). It doesn't take that long to do and then you will KNOW where your jigs are running when you see fish holding at a certain depth on the finder.
In the case last weekend the aggressive fish that woulda probably bit were probably those holding @ 5' deep. 1/32nds mighta been the ticket that day....dunno. You were probably pulling deeper and those fish never saw the jigs. Maybe none woulda bit but it wouldn't have hurt to tried something different when youre seeing fish. If all else fails then MOVE!! Don't waste you entire fishing trip trying to catch fish that wont bite.
;)