Michigan law requires that the three-year watercraft registration decal be attached to the forward half of the vessel on the same level as the registration number. Whether or not someone from the DNR notices that your sticker is not properly affixed to your boat or whether or not they give you a ticket for it is a whole other matter.
I'm on Lake Michigan and in the beginning of summer each year, the Indiana DNR stops a number of boats for inspections. I've never been stopped, but one year my son was stopped when he was out on his new 16-foot fishing boat. He received a ticket from the DNR because he did not have a Type IV life preserver (a "throwable" life preserver) on board. His previous boat was 15 feet, and he previously did not need a Type IV preserver. He had 4 or 5 "regular' life jackets on board at the time, but that didn't matter--needed to have one throwable one also.
So, maybe the DNR will never stop you, but I wouldn't take the chance. My son's fine was a couple of hundred bucks. We also make sure to have our driver's licenses with us, which can be a PITA at times.
Duct tape would also work for attaching your decals. I think that is what some of my neighbors use to attach the stickers to their ribs so that they don't lose them.
Off topic, but my neighbors and I have been to near your neck of the woods a couple of times skiing in years past. I have nice memories of New Year's Eve stays at Caberfae Peaks.