Joined: Mar 2014
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Bikes: Foundry Chilkoot Ti W/Ultegra Di2, Salsa Timberjack Ti, Cinelli Mash Work RandoCross Fun Time Machine, 1x9 XT Parts Hybrid, Co-Motion Cascadia, Specialized Langster, Phil Wood Apple VeloXS Frame (w/DA 7400), R+M Supercharger2 Rohloff, Habanero Ti 26
Go with what the manufacturer recommends. Generally it is 40mm of spacers max for most but your manufacturer might be different.
For cutting use a proper Carbon cutting blade and wear proper protection. Do it safely or just have your local shop do it and save yourself the hassle. Carbon fiber splinters are NO FUN!