I have already done some research on OMF. The Intel document is pretty complete.

Note there is a subbset called AOMF (rectype 0x06 for code) which contains the actual code.
A AOMF file should only contain absolute codesegments no reloc segments.

The problem is that most vendors extend this spec.
They create additional rec types which are propertary (Keil OMF2) (debug records)
Rigel uses the OMF format with swapped LSB/MSB for storing UINT16. :-(

You sould also read the OMF 166 specs which makes some aspects more clear.

Thomas