I've just gone for a large Superlight and I'm 5 ft 10 in. Its feels cramped with a 110mm stem and no layback post so I'm going for a 120mm. If you're riding XC (which you should be with an SL) I'd go large.
One of my mates is around 5'11" and rides a Large SL with a 120mm stem.. He is a bit of a flat-back ex roadie type so enjoys the stretched out position.. I am 6'4" and ride an XL with a 130mm stem.. The Superlight was built for XC so you need plenty of room IMHO.
Just to confuse: I'm 5'10" and ride a medium '99 Heckler (same design & geometry as SL) with a 90mm stem, risers, and in-line seatpost.
But then I decided to make a conscious decision to get away from the flat back, very stretched position I'd got used to which wasn't doing me any favours whatsoever. But then I did want to be able to drop off the back of the saddle easier, and did want my weight to be positioned further forward when I got the bike. I'm glad I did.
If you're happy with your current riding position, try both a medium and a large and see which one fits best. Trying it is the only way to be sure.
I'd guess you'd be best off with a large frame and in-line seatpost, but it's just a guess. I haven't seen your riding style, and don't know what you want the bike for.
Bear in mind that a riding position is something you get used to. Don't try to replicate your existing riding position if you're not 100% happy with it!
Thx everyone I'll come clean and admit I bought a medium in the US. It's fantastic speeding through twisty woods etc, but feels a bit small if I'm doing 25+ miles XC. SC say they'll swap the front triangle for $250 so I think I will go for the change. Teach me for being smart. Impressed by the 1.47am.
