I raced across the Gulf of Mexico in the middle of the summer. I was glad for every piece of equipment I had with me.
West Marine's best bibs
Heavy Offshore Jacket (borrowed from the boat owner as mine was just worn out)
Tons of layers to go underneath it all
For the two days that it blew and the 0230 reefing wake up calls I appreciated every piece of equipment I had on. I would not go off shore without a full layer of protection.
Not that even the best equipment will keep you dry, but will lessen the quantity of water from each wave over the bow that will make it all the way down to your skin. This allows the water already inside to at least warm up a bit. There could be days of brutal weather and foulies would allow you to spend more time in the cockpit and be more alert as a result of comfort.
But then again if you are cycling in December in Canada in a Kilt, you may be of heartier stock than me. Might I suggest a heavy wool kilt for the passage and a sport kilt for the time on the island.