I sent a copy of the putative lyrics above to Jim Payne, who recorded the song. He replied:
'Cape Bauld is down towards the tip of the Great Northern Peninsula [of Newfoundland]. I have two printed versions of this that Lem supplied. On one it says "supple" and the other says "subtle". I think I always say "supple". Also, on one version he says "ween", on the other "trow". I've heard him sing both, but I use "ween", since that's the one I heard him use most. He had someone type up all his lyrics for him, which may account for the subtle""/"supple" discrepancy, but there's not much room for that with "ween" and "trow".'
So I guess we can please ourselves with those choices.