I'm not exactly clear what you are trying to do ... can you give a little more information? If you could create two buildings in QGIS and then post the zipfile here along with the dimensions (and height) that you think they should be, I can try to modify the plugin to do what you need.
It's possible (or even likely) that the height data is in the extended values of the PolygonZ data and not in the associated database file:
Double Box // Bounding Box
Integer NumParts // Number of Parts
Integer NumPoints // Total Number of Points
Integer[NumParts] Parts // Index to First Point in Part
Point[NumPoints] Points // Points for All Parts
Double Z Range // Bounding Z Range
Double[NumPoints] Z Array // Z Values for All Points
Double M Range // Bounding Measure Range
Double[NumPoints] M Array // Measures
The last four parameters may be holding your height data ... posting a simple example will help me figure out what's what.
The basic instructions are in the header of the plugin ... I'm posting them here in case you are unsure how to open the plugin for editing:
# Two files are needed to properly import a shapefile:
# example.shp (shapefile containing polygon information)
# example.shx (shapefile containing index information)
# A third file is necessary if height data needs to be added to the 2D shapes:
# example.dbf (dBase file containing attribute data)
# The importer currently only imports type 5 shapefiles which contain polygon information
# with (possibly) multiple parts. Wherever more than one part is encountered, it is added
# as a hole in the parent polygon. Each polygon is grouped and named with the index value
# appended to the specified name (if no name is specified, only the index number will be
# used). The default name is the time that the importer was launched in the format of:
# The default scale is set to 1.0, however, if the program crashes with a too few points
# error, it can be increased as needed. Inspection of the bounding box values compared to
# the real-world size of the box should provide a rough guideline on setting a proper
# scale factor. Note that the initial bounding box values are taken from the shapefile
# itself and are not scaled.
# A good approach to large datasets is to import only the first 1000 records or so and
# then overlay a map to determine the bounding box you want to use for all the records.
# TIP: before starting the import, create a short line at the origin to use with the
# tape measure tool to determine the co-ordinates of the bounding box.
# 3D height data is available in associated example.dbf files, but each requires a
# different schema map and field names to match. However, in lieu of that, each imported
# polygon can have an optional height applied to it by entering the height where
# indicated (100.0 or so is a good start; you can always scale the groups when done with
# the import).
# Larger imports may consume more than the physical memory available. While the import
# will probably finish someday, it could take figuratively forever. In this case, the
# following two lines should be commented out where they appear in the code:
# @@model.start_operation("Import Shapefile",true)
# This will run somewhat slower, but it will finish in a reasonable amount of time.
# Shapefiles for most countries and states can be found at:
# Click on the link to download shapefiles. Unzip in a folder and then launch the
# importer, browse to the *.shp or *.shx file, and select one of them (either will
# do - however, both file types need to be available in the same folder).
# Version 3.0a introduces database support for building heights. Once the files have been
# selected, choose "Yes" on the dropdown for Database and on the next screen select the
# field from the choices. The height value should work with any numeric format. All
# heights will be scaled by the overall scale factor. If the heights are not proportional
# simply select all the groups and use the scale tool to adjust the z height.
# No smoothing is performed, but once the buildings are created, select all of the groups
# at once and apply the smoothing tool to any one of them to smooth all of them.
# Files obtained from:
# will work with the "HEIGHT_ROO" value from the associated database.
# Files obtained from:
# will work with the "HEIGHT" value from the associated database. Other datasets that
# provide height values will usually be noted in their schema dictionary.