@ general
I thought that short amount of line was not enough either, but let me explain how we came upon it. I was fishing a lake in northern WI that is about 2,000 acres and has a HUGE 6-7' deep flat that has clumps of weeds everywhere (one of three lakes where outboard motor trolling is legal in the county). We happened upon this lake and this flat while ice fishing. We went back in the spring for the walleye opener. After casting spinnerbaits and swimbaits for about 2 hours and getting nothing, I decided to try trolling the flat. I started with rattletraps, spinnerbaits, and swimbaits. Nothing....and spinnerbaits and rattletraps kept getting weeds. I got tired of reeling in 40 yards of line every 2 minutes, so I shortened the line let out. Then, I threw on a #7 shad rap and within 2 minutes I landed the first northern pike. I switched three lines (trolling four) to shad raps and caught a dozen northern pike (18"-30") and four walleye (18"-22") in the next 1.5 hours. If I was not cleaning weeds from the lure, I was taking a fish off. This technique is a lot of work since you are always messing with the lines, but it works. It is definitely not finesse, but sometimes fish react to brazen tactics. Think of all the water you could cover going 2.5-3 mph with four lines running....most fish will get out of the boat's path, but the more aggressive fish will stay hunkered down in the weeds and sometimes that minnow bait is too tempting.
I am headed "up north" again tonight for a 3 day trip. I will be on this lake tomorrow morning and I will be trolling shad raps 6'-8' off the back of the boat. I will report results in a few days.