Honestly, I would use the flower nail trick. It works wonders and if you don't like that idea, have you ever just taken a piece of cardboard and pushed the middle down? That works well too, just make sure to do it when it's hot. Or you can level it. But the flower nail thing is awesome. I keep the temp at 350 degrees, I don't like it at 325 as it take way too long!!
Another thing, (I just found this out as well) Have you ever tried the Cake extender recipe??? I tried this for the first time last night w/out a flower nail and it baked so PERFECTLY even I was dumbfounded!!!!!
AND your cake comes out soooo moist. It's a little dense but sooooo good. Hope this helps!