I have the FL-18 and always use the bottom lock feature, as it shows the bottom 6 feet in split screen. 90% of the time not needed, but nice to have. The best time this comes in handy is when 2 guys are fishing one shanty, drill 3 holes and both guys can share the flasher. In regular mode 2 lures and multiple fish on the screen become a blurr. In bottom lock one guy works just a little higher than the other and you can see both lures and multiple fish. Most guys I fish with love the marcums as they are quieter and seem to be more crisp in detail. The only problem with the Vexilar is mine sucks in water less than 8 feet. I plan on getting a second flasher and am considering getting the LX-3 for shallow water and when I take extra people out with me or getting the ice-ducer for one of my old hds5's. Does anybody have anything good or bad to say about using the hds5 in flasher mode?