I had a very long discourse back and forth with them last winter as my partners do not have a gel coated smooth surface so they actually recommended I not use there product that I had bought already.
The directions say it will actually shrink a couple thousands of an inch so I dont see how it would swell.
As already mentioned by someone the concept
is to leave it on the mast and it self aliens back up..They never said anything about cutting it in half...I have to re pull my mast soon so I will be modifying the partners to properly take the spartite..which is to have a slight taper for ease of removal
Below is a drawing I sent them to compare and clarify what they recommend to have ( top ) to what I have and wanted to do but told not to.( btm )
Hope that helps.