It’s good fun building these and they’ve designed the cable clip points and the brake mount position at the back really well.
Me, I had upgraded from my old GT ID5, so I ripped off the forks, wheels, cranks from that, and did some upgrades with new brakes, changed to 1×10 so new mech & shifter.
BB shell doesn’t need facing, just clean the threads with a wire brush and slap on what you like (my cranks were GXP so just got some new GXP cups. Went on solid and works great, no play).
Take care with the headset. A headset press is the ideal thing to use, but take it easy and watch it’s not going at funny angles. Don’t worry if it makes odd cracking sounds! Carbon is very tough stuff, but does sound odd.
Only issue was the short head tube. Though about cutting the steerer, but that would put me too low on the front, so just stacked the stem up higher and went with bars with a little rise. Went with the 16″ which is even shorter (note that there’s a compatibility issue with a couple of tapered forks I think), but the 16″ has the right reach for me. Normally I go with 18″ and they’re shorter reach than the c456.
End result, lovely sleek stealthy bike (went for undecaled matt black). It’s a spare toy for me but do love chucking it about.
Oh, and the seatpost – use some carbon assembly paste. Ideally don’t use a shim as seen reports of many who end up with them stuck in. If you use an alloy post definitely use the paste, same goes for the bars. Carbon + Alloy can in certain wet/salty conditions result in the two bonding together, the paste adds a protective layer and regardless the paste reduces the amount of pressure and torque required to clamp things on, whatever the material. Certainly helps reduce seatpost slippage which I found happens a lot with the carbon frame.