English to Portuguese Bus/Financial Economics Financial products

I'm looking at a list of complex financial products described as: inverse IOs, inverse POs and forward-inverse IOs. IO is an acronym for "interest-only" and PO is an acronym for "principal-only". In the inverse mode, those products are payed inversely related to market rates. Now, as for "forward-inverse", I can't find any clue to what it means, and THE Allan Greenspan himself calls forward-inverse IOs "mind-bloggling creatures". I would appreciate any help. :D