You share the same passion I have, I want to see a picture of your 20-30 pound northern! Tip-ups are the way to go, as is heavy spider wire or fireline, as long as you wear gloves, and loooonnnggg wire leaders are the rule because they will roll and cut your line. We use quick-strike rigs, if you don't know what they are, ask and it will be revealed. In NE South Dakota, where we fish, smelt will out fish every other bait combined, hands down, and I don't know why it wouldn't where you're at, your lake sounds much like our lakes. Find a shallow bay in early ice, hang that quickstrike down with one big smelt or two little ones, and add a teaser minnow on each treble, hooked through the tail so they wiggle more. Find bottom with a big weight, then adjust the tip-up so the smelt will hang just above the bottom an inch or two, and WAIT. It is a waiting game, and one or two flags per day is not uncommon, but neither are twenty-plus flag days, just depends on the weather. We haven't found any water too shallow, one of our favorite bays off a big lake had only 8-12 inches of water under the ice in the deep of winter and we still caught lots of big northerns. My secret tip is this. DON NOT RUN TO YOUR TIP_UP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! We have found that when we run to the tip up they will often drop the bait and leave, especially if they're bein picky. Take your time and walk normally to the tip up. If it took line and it isn't running, gently tug until you feel tension, if you don't feel tension, just leave it set for at least 5 minutes, they often come back, or they're running back at you. Give yourself lots of line on the tip-ups, you wouldn't believe how fast they can burn line off of a spool. With the superlines, make sure that you don't horse them in, they have zero give and you will tear the hooks out, if they want to run, let them run, it's more fun that way anyhow. When you get them near the hole, be patient, wait for the northern to let you guide it's head to the bottom of the hole, and once it's started up the hole, give em hell! If you let them slip back down you might be in for another long fight or a lost fish. If the treble hangs up on the bottom of the hole, don't force it, the fih will generally work the hook loose on it's own. I love fishing for northerns with tip ups, if you really want a rush, reserve once legal line for yourself to jig with, you haven't lived until a 15 pound northern hits your jig line with 18 inches of water under the ice!
Selmer
