They said many organisations were "caught in a double bind" - facing spiralling debt if they stay in the scheme or having to meet "enormous buy-out debts" in order to withdraw from it.
They want to withdraw as little as possible in order to let the assets expand but also want to donate some or all of the required payout directly to charity.
Although Tuesday was the final day for Mr Akin to withdraw from the race without a court order, he did not categorically rule out stepping aside at a later date.