Ferry Insurance
I have just been in this situation. My ferry pilot had done the requisite number of 5 single engine crossings but they would not count a further 16 twin engined crossings and they would not insure if only Twin Crossings had been made. Bizarre again.
As someone else was taking the risk I was obliged to pay the premium and so I ended up paying 1000 euros for the ferry flight from Canada to the UK. The journey took three days.
If I was doing the trip myself I would not have bothered. If I crashed then I would more than likely have gone down with the ship and being single no one else to support.