After hearing from some market participants about certain unintended consequences, the Financial Industry Regulatory Authority decided to revise its earlier proposal to establish margin requirements for to-be-announced transactions to accommodate smaller players in the market. Last week, its board authorized FINRA to file with the Securities and Exchange Commission the revised amendments to FINRA Rule 4210 (Margin Requirements) to establish margin requirements for TBA transactions (including adjustable-rate mortgage transactions), specified pool transactions, and transactions in collateralized mortgage obligations, with forward settlement dates. The proposal is...