ORIGINAL: flyX
You also might consider making a hatch for the fuel tank.
it's really easy...just cut that piece on the bottom or add little pieces of hard wood
so you can just use screws to secure it , instead of gluing it.
This way you'll have easy access to the fuel tank and the bottom of the engine.
In the 4 Star a hatch really is not needed since the tank is easily accesible from inside the wing saddle opening. Hatches do 2 bad things for the airplane:
1) they weaken the box structure
2) they have seams where oil and fuel will get inside the fuse
As long as the tank can slide out the back, you never need a hatch. And as for accessing the bottom of the engine, Why would you need to? 2 and 4 stroke engines are managed from the top unless there is something more major to work on, and in that case you would remove it from the plane.