I'm in the process of building a rampage as we speak - just got it planked last fall, going to try and get it flipped and have some framing topside by end of this summer. I too wanted more seating and in a turns-out related matter, more free-board, so I did two modifications - the boat is stretched 10% to 20', and "raised" 4" everywhere-this also widens it by 2-8 inches depening on the angle of the side planking. I should be able to comfortably seat 4 adults and 4 small kids, or 6 adults, or 4 larger adults, with no one facing or sharing space with the engine. In response to your question, it seems frank has done a number of things. I'm not *quite* good enough to say for sure, but i'd say the dash is right about where it's supposed to be - i.e. the steering wheel is the right location forward. He's definitely modified the deck, and even the entire sheer profile of the boat (notice how it flares out around the front corners of the seat and then cuts in abruptly - it doesn't normally). You'd also need to strengthen it quite a bit, since you loose strength from the lack of deck and gain load from the extra people sitting there.
PM me if you want more details about what I did to make mine bigger or how the projects going in general - I wouldn't want more then 6 people in the boat as it starts to get a little heavier then it was designed to carry