Given that there should be room for the wedges to go in, I'd be very surprised if the chock would swell so much as to bind the mast in place. How about putting it [the mast] in either without the wedges or with them only placed there by hand, to be adjusted frequently until everything has stabilised again. Another possibility is to place rubber wedges [sold for holding doors open] in place of the wooden wedges until stability is reached. Does the split need to be sealed up to prevent a deck leak happening? Peter.