That's quite a long voyage you're planning with the mast down.
1) I would support the mast at three or four points, the closest you can get to the sticking out ends the better.
2) Both ends need severe padding, I would suggest you obtain some flat 5-6mm rubber sheets
and wrap it around the mast's ends securely. Then paint
the rubber bright orange!
And a further comment, make sure you have many oversized fenders / tyres for the many commercial shipping
locks you will be encountering. And don't forget a place to hoist the courtesy flags