I don't have a View but mine is identical to the View H floorplan. Like you, our jacknife sofa sloped down badly toward the aisle and was generally pretty lumpy and uncomfortable as a bed. I removed the cushions, added some steel tubing as supports, tried to level it as much as possible, and covered it with plywood.
We initially tried using a futon mattress but found it really heavy and difficult to deal with. After returning the futon, we started asking around at local furniture shops and found one that could get custom cushions made nearby. The cushions cost us around $400 but we are really happy with the result. I still have the OEM cushions and they can be put back if it's ever necessary.
Here's a link to one of the View owners who went the futon route:
https://groups.yahoo.com/neo/groups/View-NavionTech/conversations/topics/33982Note that this post is in the Tech forum and you'll probably need to join if you haven't already.