I'll just repeat what the other "skinny" owners have said here. I'm 5'11", 145lbs. and have a 31" waist. The seats are nice, but designed for a bigger person. I fit much better into the Corrado seats that have been transplanted into my 93 Volkswagen Fox.
I probably wouldn't have been much worse off with the "S" or standard "SE" seats, which really aren't bad at all.
I did take the Focus on a 350-mile round trip this past weekend that included some great mountain roads and the seats were comfy and held me in place as much as I expected them to given my previous comments.
Also, I'm not a huge fan of the fabric. It seems overly athletic and kind of cheap. I like the contrasting grey and black, but don't particularly like the pattern. I do like the white stitching and I do, in general, prefer cloth to leather or vinyl.
Just my 2 cents on this subject. ...
2012 Ford Focus SE, ╠╬╝, Sport Package, Ingot Silver. 1993 Volkswagen Fox. Formerly: 2005 Focus ZX3 SE, ╠╬╝, Pitch Black, SVT suspension.