You mean around 25'?
The attic and the roof are nowhere near equivalent locations, even at the same height. Everything we've been talking about is in the free air. Attics are a whole other story.
You can get to 50' from a 30' roof peak. Buy a 20' extendable mast, and mount it to the peak with a mount like this -
http://www.antennapartsoutlet.com/Pa...DGEMOUNTS.html Run guy wires down to the roof edges.