The corporation shall prescribe regulations to establish a supplemental program to guarantee benefits under multiemployer plans which would be guaranteed under this section but for the limitations in subsection (c). Such regulations shall be proposed by the corporation no later than the end of the 18th calendar month following
September 26, 1980. The regulations shall make coverage under the supplemental program available no later than
January 1, 1983. Any election to participate in the supplemental program shall be on a voluntary basis, and a plan electing such coverage shall continue to pay the premiums required under
section 1306(a)(2)(B) of this title to the revolving fund used pursuant to
section 1305 of this title in connection with benefits otherwise guaranteed under this section. Any such election shall be irrevocable, except to the extent otherwise provided by regulations prescribed by the corporation.