Best way to determine a reasonable rate of interest for final 3121(v)(

[Guest johnnyG]

Treas.Reg. 3121(v)(2)-1(d)(2)(i)© does not define what is a reasonable rate of interest for taking into account income attributable to an account balance plan (for purposes of the non-duplication rule). What authority could be used to test a rate such as the long-term applicable federal rate or, E.G., 110% of the LT AFR? Considering that the AFR's, especially the mid-term AFR, are relatively conservative, what are the guidelines?