im toying around in hammer. i used a treeline and set it as func_illusionary and set the FX value at 255. the top of the brush (blue area) is outlined when i compile it, though.

here (http://img.photobucket.com/albums/v68/superfanthony/brecourt1.jpg) is a screenshot of what i mean.

how can i prevent that from happening?

1) Lower the brush a tad...perhaps the bottom of the texture is showing on the top.
2) Place the null texture on all faces except the front...perhaps the top and sides are also the tree texture.

will try. thank you, sir.

thought id mention (incase you didnt know) in order to compile with null textures you need merl's custom version of the zoners tools (which can be found here: http://collective.valve-erc.com/index.php?go=mhlt)