Welcome, Michael! Tasmania is a place I'd like to take my LF. That should be a great trip! I have only been to Sydney and north and only briefly. One other possibility is a 120 roll back for the 4x5. For the weight of the rollback, you get a medium format camera with movements as well as a 4x5! I used this set-up up north near Darwin many many years ago.
And welcome Tom! Also many years ago I was using a Turner Reich convertible with no front element (for a focal length of 28"). I was photographing the lunar eclispe in the upper foothills of the Sierras Mtns (California) ...one sheet of 5x7 film with an exposure every 10 minutes. Ended up with one long streak after the 5th exposure -- the shutter in the damp and cold had not closed...discovered as I tried to take the 6th exposure ten minutes later.
One reason I have heard why a convertible is not as sharp with one element removed is that the lens loses some of its ability to focus all the colors on the same plane -- especially blue. So a yellow filter is suggested to reduce the blue light for sharper images. And I suppose if a yellow filter could be screwed in where the front element usually goes, that would protect the shutter from the elements as well.