[itsme]

For ChordGrids "Auto-Size Font" seems to calculate the maximum font size that is possible before characters start overlapping. This works pretty well in most cases, but I came across examples where it still goes wrong.
for BengerzBrauneBrieh_SHe_ABC.pro the calculated font size is too big
   
and for ChordsInComments.pro it is much too small
   

[itsme]

Sorry, i have to correct me regarding "for ChordsInComments.pro it is much too small". 
MobileSheets works correctly, with {start_of_grid 6+4x4+1} the right margin (width = 1) is not wide enough. So MobileSheets makes the font small enough so that the text fits anyway. 
Here's an example with {start_of_grid 6+4x4+6} which defines more appropriate margin widths