Mountain Biking - Stumpjumper FSR sizing

I'm in the talks with a guy who has a 2004 medium Stumpjumper FSR for sale... really cheap too.

Thing is, I'm 5'11"-ish. Could I make do with a longer stem and seatpost?

I plan on riding mainly XC-type trails, some AM.

I am bout 6' 1" and a few months ago bought a Large 2006 Specialized S-works 120 FSR frame.
It has the laid back Thomson elite seatpost and a 100 mm Thomson X4 stem.
The FSR seems to have a shorter top tube. I have 2 other 19.5" inch frames and would say that the FSR
seems a little more "compact" in the reach dept. It seem to have a larger Drop to the handle bars as well,
feels a little racier. But it still fits fine, and the FS sure rides nice.

At 5' 11" I would say a medium would be on the verge of too small, especially if you have a longer torso and shorter legs,
I would ride one first.

I'm in the talks with a guy who has a 2004 medium Stumpjumper FSR for sale... really cheap too.

Thing is, I'm 5'11"-ish. Could I make do with a longer stem and seatpost?

I plan on riding mainly XC-type trails, some AM.

I think 5'10" is about the cut-off for medium.. At 5'11" medium will feel too short for steep climbs and a bit of a handful if you have to put a long stem on it to make it fit.

I'm 6"4 riding an o4 Stumpy FSR with an XL frame. My I have a 30 (?) mm offset seat post & 120 mm stem with the seat kicked up pretty good. The bike is a very comfortable ride with this setup, but believe I'm at the edge of the spectrum with the XL size frame. That being said, It sounds like you are taking a gamble going with a medium.

Oh well... I guess I'll just have to pass on it.

Oh well... I guess I'll just have to pass on it.

Good idea, too many people figure they'll deal with it if the bicycle is too large or small. Getting something that fits correctly is the best way to improve your dollar to fun ratio.