I'd use two lines with a hard thimbled eye in one end of each.
Essentially the lines are secured at the mast, pass out well chafe guarded through the chocks on either side, and are shackled to a larger shackle that can take the tow line. The rig should be long enough that you can easily attach the tow line from a safe place back on the foredeck and then pay it off.
How long depends on how you attach to the mast. I'd make long enough for three turns around the mast with each line, then each gets three loops of a tuggy's hitch and finish with a simple taughtline hitch as a keeper at the end. This arrangement will actually come undone without cutting line at the end of a long tow.
Big point is serious chafe gear.
The tow line should be long enough that it will not be leading up from your bow, but it may surge up if it's short enough that it's tight and proud of the water as you come over a crest and the bow plunges on the other side. For this contingency, you may need some sort of keeper to hold the line in the chock or, better yet, closable "panama" chocks.
G'luck
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