126.0 (而) would be a natural way to look this up and should be an alternate radical. However, the meaning of this character is "two" and 而 is phonetic, so based on IRG rules, the best radical might be 7.0 (二), SC=9, FS=1
I'm not sure what IRG rules you are referring to. However, IRG PnP §2.2.1 d. (5) c) states:
"If the technically correct (aka semantic) radical for an ideograph hampers its discoverability, or is region-dependent, the primary radical shall be assigned as though made by an ideograph expert who is neither a specialist in the history of the Han script nor familiar with ideograph etymology. The technically correct radical can be assigned as a second radical. Both are shown in the code charts, though the primary one serves as the basis for ordering within a CJK Unified Ideographs block."
Therefore, in this case the primary radical should be R126 而.