True Type Font : Mm Symbol AGSO Letters

Hi,

I have letters in Hatch Sets that I would like to add, such as Lt (to represent Laterite), and Lo (Loam).  

The letters we would like to use may not be representative by AGSO letters, however adding extra letters would be pretty good to add to the Fill Pattern.

Do we have any ideas on how to add letters to Hatch Set True Type Font letters?  I know there is a "DXF Export Supported", but possible alteration of the DXF file is not obvious.

Any help appreciated.

Kind Regards

Dave