Might as well post the relevant bits of the script as it stands,so you can see what I was doing.

For the Smart+ script this is how I find the datafile:

    ...
    # Locate the smart plus datafile
    sDatafile = os.path.join('Runtime','Python','poserScripts','3DCheapskate','SmartPlus','SmartPlusData.txt')
    smartdatafile = locateDataFile(sDatafile
    ...

...and this is the locateDataFile() function, which checks the Poser applocation first, and then each mapped runtime in turn

    
# sFilename is the path in OS-specific format starting at Runtime
def locateDataFile(sFilename):
    locatedfile = ""
    filetocheck = ""
    global sTempErrLog
    # Check for the data file in the application location (Poser 6 PoserPython doesn't provide a method to scan mapped runtimes)
    poserpath=os.path.split(poser.AppLocation())
    filetocheck =  os.path.join(poserpath[0],sFilename)
    if os.path.exists(filetocheck):
        locatedfile = filetocheck
    else:
        # If it's not found then log it so we can inform user later if necessary
        sTempErrLog = sTempErrLog+"nFILE NOT FOUND: "+filetocheck
    # Check for the data file in the mapped libraries (if already found we still check for multiple copies, but use the first one we found)
    try:
        aLibs = poser.Libraries()
        for lib in aLibs:
            filetocheck =  os.path.join(lib,'Runtime','Python','poserScripts','3DCheapskate','SmartPlus','SmartPlusData.txt')
            if os.path.exists(filetocheck):
                if locatedfile == "":
                    locatedfile = filetocheck
                else:
                    poser.DialogSimple.MessageBox("Multiple 'SmartPlusData.txt' files found")
            else:
                # If it's not found then log it so we can inform user later if necessary
                sTempErrLog = sTempErrLog+"nFILE NOT FOUND: "+filetocheck
    except: # Poser 6 will always cause an exception because the Libraries() function doesn't exist
        pass
    return locatedfile

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident. And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU or something else.
*soon only to be available in two flavours -  DAZ and Renderosity