I too have the Corbin Fast Gun on my Roadster and love it. Everything they have said is true, it is hard and it does take about 5,000 miles of riding to completely conform to you, but I enjoy it. I also know that other hate them and believe you have to get what works best for you, that's why there are so many choices.
Very possible, haven't had a chance to do any longer trips like that. I think the longest I've spent in the saddle is probably 6 hours? Problems with living on an island.
I went to a store that sells skins and furs. I just purchased a full sheep skin and cut it to fit. it was big enough to make covers for 2 bikes rider and pillion seats. And there was some left over to make backrest pads too.