I use line counter reels. I usually start at 60, 80 & 100' out. If no go at that depth, I increase each rod another 20' until I get a few bites. I adjust my depth to the hot pole or poles. You get a feel after awhile of how deep your cranks run at certain speed and line out. I don't worry about length of line from rod to water. If you start getting bites at say 80'. I will adjust other rods to 70 and 80' to fine tune. I watch my fish finder all the time. Crappie go up and down during the day. Mainly because of sun.