symbology - qgis place marker in dashed line

I would like to create a marker line in which a font marker is placed within a dashed line space at equal intervals. Something like line-style-with-alternating-dots-and-long-dashes

c - c - c -

I can get this to somewhat work by creating a marker line with a custom dash pattern: Dash=10 Space=3 mm Then setting the font marker with a interval of 13mm and offset of 11.5 (midpoint of space).

The problem I have is that it appears that when the line become more complex there appears to be a misalignment of the dash space and marker offset

Regards