If the boat lacks the weight to drop itself through the ice, there is the problem of getting off. Even if the stern is not sufficiently submerged to flood the back end, there might not be enough power to pull it back off the ice. The surface of the ice might not be as low-friction as you think for something small and light that has just flopped onto it dripping wet, runny water that freezes onto the surface. I managed to give myself a scare with my Snowberry like that several years ago.
arrow5, how did you get your springer back? How did you manage to get it there in the first place?