This is a great plane but it is hard to get the tank in center with the carb spray bar. The only way I found was to cut one of the cheek pieces of and mount the engine sideways. It will run mounted upright though but not as well. Any old modler will tell you to make sure the tank is centered with the tank. Yes there are some people that will tell you it doesn't matter but that is not true.

The distance from the firewall all depends on the Center of Balance. If it is nose heavy mount it as close as possible, if it is tail heavy mount it as far away from the firewall as possible. This will help balance the plane. This is a great second plane but make sure you can fly a trainer well first. The SE can be very fast with the 46 or larger engine.