Eprocurement 9.1 direct connect supplier Outbound Request cxml PO transfer Program options

Trying to figure out how transmit both Header comments and line item comments to direct connect supplier in cXML that is generated by the transform program.  We've always used PV_PO_CX_REQ but have realized that line item comments though they show up on a printed PO and when looking at it on screen, the cXML that gets sent to supplier omits the line item comments the user adds to the requisition and to the PO. found document 1390686.1 that says they aren't transmitted and also references PV_PO_CX_REH and PV_PO_CX_REL.  I'm trying to find info on the differences between these 3 programs and if one of them will send header comments as well as line item comments. Thanks for your help in advance