I'm not a fan of floats for ice fishing Walleye. I like to go down to bottom often and tap the bottom and stir it up a bit and bring it up slowly. A good percentage of my fish are tagged coming just off bottom slowly. I could see them being effective for Perch or trout maybe.
Interesting, I like the idea of the line side being underneath the ice. I used to use slip bobbers a lot especially for perch when the bite was lite but kind of moved away from them as it got a bit annoying unless the conditions were optimal (warm), and the ice build up around the float, line, and stopper was manageable. I take the whole family out fishing a lot as well and honestly have found the best way to battle a light bite is through a camera where they can actually see the fish inhale the hook. They look like something valuable to add to the arsenal for certain situations though, couple questions. How quick are they to set up? Do they clip on or do you have to run the whole line through? What do you do with the float when you hook one and are reeling it up?