It is not recommended that you change the stitching values (stitch length, spacing, etc) of these alphabets at all.
Other Chenille alphabets have been designed for use within certain size ranges and of these some Perpendicular Fill alphabets allow object properties such as stitch length, spacing and offsets to be varied.
Tip : To change stitching values such as stitch length or spacing select a join method other than As Digitized in the Object Properties - Lettering > Sequence dialog.