I don't think you'll notice any difference if you mount it a little to the left. Most planes can stand a little right thrust anyway.

30 years ago, when engines were much less powerful, many airplanes came with right and down thrust. Then, with smaller props and higher rpms, everyone gravitated to 0-0 set-ups. Now, you are seeing right thrust again, in particular in 3D planes.

You didn't say what engine you were using, but if it matches a popular OS engine in muffler mounts, they have muffler extensions for the .46, .61 & .91 that I have used. They may have them for the smaller sizes. Go to Tower and search for them.