The optimizing calculation only takes into consideration the current year taxes, which includes the current year repayment of OAS, but not the following year's clawback.  If you are sure that she will have the clawback next year with the pension splitting but not without the pension splitting, it might not be worth it for that amount of savings.  I also consider the effect on a taxpayer's requirement to make instalment payments when determining if the pension split is worthwhile.