When you pull the tube tip away it tends to leave long a thin web (strings of goop) that needs to be dealt with. It cleans up with solvents. The butyl tape is very "grabby" and could be pressed in place like clay. The big question is whether you would get a good seal without fully separating the halves and compressing the butyl. Like any sealant, a layer of dirt, grime or salt crystals could give you less than perfect results. Probably no harm in trying.