I'm removing an old(10year old decal ) and replacing it with a new one-same size and logo, I have heated and scraped the old one off with a plastic putty knife and a hair dryer and there remains a lay...
The decal protects the gelcoat,it is not uncommon to have a higher area where the decal was. If a decal is truly stuck you can stack it,It is done on boat names and truck doors all the time. I wouldn't unless it is completely covered by the new one with a few inches all the way around. You will see the edge through the new vinyl. You can do it but not really the best idea.