I’ve just built up my C456.
1. Headset was tight to fit. I don’t have a headset press, but 10 minutes cursing with a rubber mallet saw it done. I got the superstar headset with integrated top cup/external bottom cup – type 2 I think.
2. I have fitted a SLX 2×10. The rings are slightly tighter than ideal to the chain stay, but not as bad as on my old Cannondale rz. Due to the flaring at the bottom of the seat tube, a hi clamp front mech is required. I couldn’t get it as low as I wanted, as the cage interfered with the chunky chainstays, but advice from the STW massive was that more clearance was acceptable/required on a double (was advised to fit it as if a 3rd ring was there) and it shifts perfectly.
3. Cable routing are a little interesting!!!
4. It works great for me with a Talas 2010 140/120/100 tapered fork. There are some issues with some tapered Rockshox apparently.
5. My seat tube had a restriction, which turned out to be the rivet from the front mech cable boss. On advice from on one, I filed this down, and all is well!!
6. It is VERY light :-))