Problems with LineStyle Dash-Dot definitions in standard.sod

Hi all,

I'm working on import and export of Dash-Dot LineStyles. I have not yet 
checked whether it does not break a unit test. But from visual 
appearance and file format these works already:

Roundtrip in pptx and ppt format with MS Office preset dash definitions.

Roundtrip in pptx format with custom LineStyle definitions as far as 
possible. There are some principle incompatible things: OOXML dash 
length is always relative to line width, but ODF allows absolute dash 
length. OOXML allows a arbitrary number of dash kinds in one definition, 
but ODF allows only one or two. OOXML allows different space length in 
one definition, but ODF has only a single space length.

Now my problem:
The current set of LineStyles in standard.sod is a mix of styles with 
absolute dash length and relative dash length. None of the definitions 
corresponds to a MS Office preset definition. Roundtrip with MS binary 
format does not work at all.

So what to do?
Map the styles from standard.sod to a roughly fitting MS Office preset 
definition on export to ppt?

Get rid of the current set in standard.sod and provide instead only the 
MS preset dash definitions in standard.sod?

Is it even possible to use custom dash definitions in binary format? If 
so, how do you do it and is it worth to implement?

Kind regards
Regina