Plan rules.
(d) Plan rules. Plans may adopt rules for calculating an employer's initial allocable share of the plan's unfunded vested benefits in a manner other than that prescribed in paragraph (c)(1) of this section, provided that those rules allocate the plan's unfunded vested benefits to substantially the same extent the prescribed rules would. Plan rules adopted under this paragraph shall operate and be applied uniformly with respect to each employer. If such rules would increase the reallocation liability of any employer, they may be effective with respect to that employer earlier than three full plan years after their adoption only if the employer consents to the application of the rules to itself. The plan sponsor shall give a written notice to each contributing employer and each employee organization that represents employees covered by the plan of the adoption of plan rules under this paragraph.