It is not a Drop shadow but is a BLOCK shadow. It appears that it may also incorporate a tiny outline around the lettering. (the photo seems to show an outline although the text vinyl appears to have been installed even with the top of the outline)
FlexiLetter should provide a variety of shadow styles including BLOCK (Effects > Shadow). The sub-menu drop-down in Design Central's Shadow tab will permit various Block shadow effects including incorporating an outline as a component of the shadow. It also permits control if the shadow extends behind the text, abuts the text or leaves a space between the text and the shadow.
One thing I see within your sample is the holes within the 'O's', 'D's' and 'A's' are filled in solid with the shadow colour.
To do that:
-Apply to the text a Block shadow with backing but without an outline.
-Separate the shadow from the text.
-Apply a small 'Contour' outline with backing to the shadow only (Effects > Outline). Even if the text does not utilize an outline, use the Outline tool set to 0" so that the lettering holes will be filled.
-Separate the outline from the shadow and ensure both the outline and shadow are the same colour.
-Weld the shadow and outline together thereby creating one piece of vinyl for both the shadow and outline.
All the best.
Mark