Then I guess I was fooled by the scenery

will have to look for another way to model custom trees. Any ideas?
Why settle for what IIRC the legacy SDK called "Rotate-To-Aircraft" 2D objects when you can make a 3D "cross-plane" object in Sketchup ?
To test this work-flow feasibility as a "proof-of-concept" for yourself, download and install Rhumbaflappy's excellent "
Center_Group_Bottom" Sketchup plug-in:
http://www.fsdeveloper.com/forum/showthread.php?t=71321
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EDITED]
Then, in a newly initialized Sketchup session... with the default "person" as the
only object, and in
ISO view:
_1.) Sketchup Menu > Edit >
Select All
_2.) Sketchup Menu > Edit >
Explode
_3.) Sketchup Menu > Edit >
Select All
_4.) Sketchup Menu > Edit >
Make Group
_5.) Sketchup Menu > Edit >
Select All
_6.) Sketchup Menu > Edit >
Copy
_7.) Sketchup Menu > Edit >
Paste In Place
___a.) Sketchup Menu > Tools >
Protractor
___b.) Hover Protractor Mouse Cursor over the
top of that "Person" object bounding box (
'Protractor' appears)
___c.) Left Mouse Click-Hold "+" marker of Protractor, then
rotate copied "Person" object 90 degrees to original; release left mouse button
___d.) Sketchup Menu > Edit >
Select All
___e.) Sketchup Menu > Edit >
Explode
___f.) Sketchup Menu > Edit >
Select All
___g.) Sketchup Menu > Edit >
Intersect Faces >
With Model
___h.) Sketchup Menu > Edit >
Select All
___i.) Sketchup Menu > Edit >
Make Group
_8.) Sketchup Menu > Edit >
Select All
_9.) Sketchup Menu > Plugins >
Center_Group_Bottom
10.) Sketchup Menu > Edit >
Select All
11.) Sketchup Menu > File > Export > 3D Model (
'Export Model' dialog opens)
___a.) In Export Model dialog, set Export Type = Collada (*.DAE)
___b.) In Export Model dialog, enter desired Export [
filename].DAE; click "OK" to save into a specified target folder location
12.) Import that Collada (*.DAE) file exported by Sketchup into a 'recent build' of ModelConverterX (aka "MCX"):
http://www.fsdeveloper.com/forum/downloads.php?do=file&id=82
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MCX should now display a 'visible' model of the textured 3D "cross-plane" object...
with all mapped textures showing proper transparency attributes.
FYI: In Sketchup, one can use custom tree textures with 'proper' transparency in the alpha channel of the texture (
ex: *.TIF, *.BMP or *.PNG) mapped onto a "cross-plane" object to make custom tree objects.
IIUC, in MCX one may wish to use 'Drawcall Batching' if a tree is intended for use as a custom Autogen object, and 'LODs' if intended for a scenery library object.
PS: One can also use this method to make other types of custom vegetation
ex: bushes, grass, etc. !
Hope this helps !
GaryGB