satin vs. running stitch.

Ok,,,,
I'm sewing the "military" or "stencil" font.

Seems I can't get it tight enough using a satin stitch, using the machines recommended setting for density and stitch length.

Should I change to a running, or fill stitch!

The default for this font is a satin stitch, which would look good if I could get it tight enough.

Any suggestions.

Location: 
United States