I recently installed a full carbon fork on my bike with a Ritchey WCS stem. I discovered that Ritchey recommends a lower torque for tightening the stem bolts on a carbon steerer than on an alloy steerer. You should see if you can find the proper torque numbers for the 3TTT Forgie stem bolts. As an example, here is what Ritchey says for my stem:

Torque specs and bolt pattern for WCS stems:

1) Torque specs:

WCS stem front faceplate with 4mm bolts
- 30-60kgfcm for alloy bars 26-52 inch/lbs
- 40kgfcm max for carbon bars 35 inch/lbs

WCS stem steerer clamp with 5mm bolts
- 60-100kgfcm for alloy steerers 52-86 inch/lbs
- 90kgfcm max for carbon steerers 78 inch/lbs


Also, my fork came with a special preload gizmo that does not scrape up the inside of the carbon steerer like a star-fangled nut would.

By the way, the Forgie is a pretty heavy stem; that's what I had before I got the Ritchey WCS, but I didn't have a full carbon fork then

Hope this helps,

David