would there be anything wrong with running a short stem and slack head angle for xc?
This is something I’ve wrestled with a fair bit. I’d describe myself as a nervous XC rider. I like to ride up the mountain, so want something that is efficient and easy to move around on the climbs. But I also like to feel comfortable on the way down, so want as much skill compensation as I can get my hands on. Of course those two desires are contradictory and the ideal compromise will be different for all of us.
So far, I’ve not found anything to displace my 26″ Five. I’ve had a couple of HT 29ers (FF29 and Solaris) that are faster uphill and I could ride either of them down anything that I’d take the Five down. But they turned the descent from something I’d enjoy on the Five to something I just had to endure (and was glad when it was over). That’s very much personal, of course and for some people those bikes are the perfect compromise.
Getting back to your original question, I stuck a 35mm stem on the Solaris, which is shorter than Cotic recommend and I really liked what it did to the handling, so it’s certainly worth experimenting.
I should point out that the Five is far from perfect, it’s just the best compromise I’ve found so far. But I’m intrigued by these newer FS 29ers that are slack at the front and short at the back.