I've always liked 5x7 contacts. I've recently started shooting 5x8 because it is slightly more panoramic. A 5x8 contact has considerably more impact than a 5x7 IMO. 5x8 is 1/2 the size of an 8x10.

Here's a link to see the Chamonix 5x8.

http://www.chamonixviewcamera.com/58.html

I don't yet have the Chamonix 5x8 camera. I've masked my 8x10 ground glass for 5x8 and use that area for composition, and shoot it on 8x10 film. After development I trim the 8x10 neg down to slightly larger than 5x8.

Yes, it wastes some of the 8x10 neg; and I have to setup an 8x10. Just thought I'd mention the 5x8 format.