Ok, so here's the proof that the Alpha X and Sigma X work brilliantly on both the original IA and the newer IAx frames, even with the pre-cut forks:
Alpha X + Felt IA Compatibility
http://www.tririg.com/...lpha_X_Compatibility
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TriRig.com
Alpha X + Felt IA Compatibility
http://www.tririg.com/...lpha_X_Compatibility
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TriRig.com