i use to use the davis rig and switched to a large flasher and a chartreuse peanut, troll as slow as possible and keep it as close to the bottom, deadly. i also would go only back from my release about 5-7'.
i just installed a lowrance x135, go to thier web site, it allows you to try any of their sounders, plus with a battery add on i can use it as a flasher for ice fishing, $399 at cabellas