The only way I can think of to do it using form is to use the Kaleidospace feature and offset the center xy in conjunction with rotating in z space about 43 degrees. I am not sure what you are going for. If this is just for a background, would it not be easier to use a precomp, offset and then motion tile the layer? Also, remember with form, when you move the camera around, the custom particle shape will always autorotate to face the camera. This may or may not be what you want.
I have attached a file for you to look out. It is CS5.
2669_bgo.aep.zip
best,
Mike
