Let me be the first to bitch. I use a Linhof 612. So at 2:1 this means I'm still homeless? What autocrat came up with 2.5:1?
For me aspect ratio has a lot to do with where you started. If you started with 6x6 then even 6x9 or 35mm can look panoramic to your eyes. I started at the other end doing 8:1 panoramics with Cirkut cameras. Coming from that extreme 6x17 doesn't look very panoramic to me.
When I shoot 617 I always crop a bit off the top to stretch the format a bit, I like a 4:1 minimum.