Finally figured it out:
Download data as GeoTIFF ->
Import into 3dem, export as USGS DEM
Import into Google SketchUp, save as SketchUp
Import into 3dSimEd and export as 3ds.
Import into Xpacker and find out that you have too many vertices for BTB. Redo the Google S.U. import with less points and try again...
There MUST be an easier way, but atleast it works. If you wan't to see how the data looks like in BTB and how I use it, see my Meadowdale project at the WIP subforum.