If you use sikaflex it will be permanently bonded I've taken transom shields out in the past stuck with sika and its pulled the gelcoat off down to the laminations
If its a hatch you may want to remove again you should realy consider a none hardening mastic or semi hardening
If its a location you can get a knife under to cut the sika if you want to be in again then fine but if not use something with less "stick"
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