Something to consider,

In pattern, your optimum fuel tank location is over the CG. This means generally about a 14" length of tank line. Most engines without a pump won't be able to draw fuel that distance easily or reliably. Also, in most Pattern birds (that I would consider a true closer to current pattern plane) the engine is inverted and requires a pipe to run down the belly pipe tunnel. This of course isn't needed, you can always cut a hole out the side of the fuse and create more drag (sarcasm LOL) But in all honesty, I'm a firm believer in that, if you are building a pattern plane, to compete, there is a reason that certain engines are always recommended for the specific purpose of pattern flying. I competed up to the Advanced level with .60 Pattern planes (Meridian's) then moved into a Legend 5 and then an olympian before switching to Jets. A pattern bird flies so true, I can't imagine interupting airflow with a big muffler hanging out the side. Whatever engine you choose, I recommend finding something Pumped and place your fuel tank over the CG. Be sure it's an engine that likes to run inverted (with a pump it really shouldn't be a factor).

I was running 13x12N's on my Y.S. .61's at about 10,200RPM on 25% nitro with a K&B "L" plug.