Ha, you know, I missed the part on the OP where he said "sound more fullscale". I was talking about just making it LOUD, not necessarily full scale sounding .

Ok, for full scale, get the RPM down, and play with the muffler. I've noticed that the Slimline mufflers seem to make even small 2-stroke glow engines sound more like larger engines, and when you match that to a bigger prop at lower RPM, you get a good result. I've done that on the .32 powered plane I mentioned, and also on my .46 powered twin engine Mossie.

I also agree that 4-strokes usually sound better in some applications. I have an old OS .61 FS that I fly with no muffler at all. It's not as powerful as more modern 4-strokes, and not as loud, but with out the muffler, it sounds nice to my ears