Actually, since it is a generic building, you don't need to make a library object out of it, if you are just placing it a few times. It can be done easily with XML. Here is the Bogota Hangar, which looks like the same one as Placerville (although I believe the one at Placerville might be longer).
<?xml version="1.0"?>
<!-- disassembled by NewBglAnalyze Sun Jan 23 15:03:14 2005 -->
<FSData version="9.0"
xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
xsi:noNamespaceSchemaLocation="bglcomp.xsd">
<SceneryObject
lat="N04 41.54651"
lon="W074 7.99551"
alt="0.0000M"
altitudeIsAgl="TRUE"
pitch="0.00"
bank="0.00"
heading="216.38"
imageComplexity="NORMAL">
<GenericBuilding
scale="1.00"
bottomTexture="102"
roofTexture="37"
topTexture="67"
windowTexture="93">
<RectangularBuilding
roofType="RIDGE"
sizeX="160"
sizeZ="40"
sizeBottomY="5"
textureIndexBottomX="512"
textureIndexBottomZ="128"
sizeWindowY="0"
textureIndexWindowX="0"
textureIndexWindowY="0"
textureIndexWindowZ="0"
sizeTopY="0"
textureIndexTopX="0"
textureIndexTopZ="0"
textureIndexRoofX="13568"
textureIndexRoofZ="6839"
sizeRoofY="5"
gableTexture="1093"
textureIndexGableY="512"
textureIndexGableZ="128"/>
</GenericBuilding>
</SceneryObject>
</FSData>
Change the coordinates to the proper location of course and the heading. You can adjust the size in size X and size Z.....just keep in mind the texture pattern must repeat, and you don't want 1/2 of a door at the end of the building. The one at Bogota has 10 bays, so apparently the length is a multiple of 16 meters.
I am using replacement textures, but I imagine it is the same for default textures.
Once you make the necessary corrections, save the text file with the extension .xml and drag or drop the XML over BGLcomp, and bingo you have your new bgl. Place it in an active scenery folder.
You might want to check out NewBGLAnalyse as it makes it very easy to extract generic objects and models from the default FS9 files. The file you will be interested in is in the main scenery folder, then the particular area folder (SAME in the case of Bogota, NAMW for California). Open the scenery subfolder and look for a bgl starting with the letters OB. NewBGLAnalyze will extract an xml file from the bgl with all of the objects and models. They will be very numerous, but if you do a search in notepad you will narrow it down pretty quick. For instance for the Bogota Hanger by slewing in FS9 I found the coordinates to be approx 4* 41.547'N and 74*7.996W. Since I know these are not exact, I entered: find "N04 and then scrolled down until I found the correct one. I knew I was looking for a building with a RIDGE ROOF so it didn't take long.
Let me know if this helps, and I apologize for the discourse if you already knew all of this.