shall only apply if the plan otherwise meets the requirements of such section and in applying such section, the date the class of participants is closed shall be the effective date of the later amendment. 206. Modification of PBGC premiums for CSEC plans (a) Flat rate premium Subparagraph (A) of section 4006(a)(3) of the Employee Retirement Income Security Act of 1974 ( 29 U.S.C. 1306(a)(3) ) is amended— (1) in clause (i), by striking plan, and inserting plan other than a CSEC plan (as defined in section 210(f)(1))