Problems adding attachment to doodad unit

I have created a building (a shop) from a doodad and I want to add a question marker over it.

I have tried using the command:
Create a special effect attached to the "?" of "my new unit" using Objects/Randomobject/RandomObject.mdl

However do doodads have any attachment points?

And then I was thinking about using a dummie unit to show the question mark, but if I create an invisible dummie the question mark will also be invisible, and if I create a very very small dummie, the question mark will be resized as well ... =(

Does anyone have a solution to my problem? :(

Either use a unti that has the locust ability and has the question mark as the unit model or create the SFX at location, not on the unit.

Hmm... the create SFX at a point was a good idea, but it ends up inside the model... Can I create a SFX a bit up in the air?

That locust thing sounds a bit drastic, but I guess that it is the only way to do it then?