The following example shows that when no offsets are given there is no gap between the faces.
<SMS_PARTS NAME="Profile-Profile">
<SMS_PART KEY="RT_1" TYPE="PROFILE" MATERIAL_LOOKUP="MATERIAL_CARBON_A" COMPONENT_LOOKUP="RT_1">
<SMS_CELL NAME="WEBL" OUTPUT_UPSIDE_FACE="base"/>
<SMS_CELL NAME="TOP_FLANGE" OUTPUT_UPSIDE_FACE="top_flange_top"/>
<SMS_CELL NAME="WEBR" OUTPUT_UPSIDE_FACE="webright"/>
<SMS_CELL NAME="BOTTOM_FLANGE" OUTPUT_UPSIDE_FACE="bottom_flange_bottom"/>
</SMS_PART>
</SMS_PARTS>
</SMS_MFG_AS_PART>