I want to convert a 25cc homelite weedwacker engine to a plane engine and I have been sitting here reading post after post and after all the reading there is one thing I know and that is I am confused.

I purchased a reconditioned weedwacker from a traveling tool equipment show in the summer. Supposedly it is a 25 cc engine but the exhaust port is not bridged so is it a 25 or a 30? The displacement is really not why I am confused. The confusion points are this.

So I take this engine (which is sitting on the table next to me) and I carve it down. Now I am left with a cut down engine and what is next is what I am asking my self.

The engine is reconditioned. Does that mean I need to install a Bowman ring?
It came with a 9mm Zama I guess that means I need to go to a 11 mm Walbro
Do I go with CDI or stay with the mag ignition?
Twister manifold seems to be a must as does a new muffler?
If I do not go with a CDI I need to have the flywheel fins cut off and the flywheel rebalanced?
If I stay a mag ingition I am looking at a boat anchor of an engine
Do I need to remove the base gasket and adjust the port timing?
Do I need to cut down the squish?
Is a 35mm (protruding from the front bearing) a long or short shaft?

The plane I want to put it on is a Birdi Big stick or an Old Timer. These are 9 lb planes with 80" wing spans which should support the square inch to weight recommendation.

I would really appreciate some guidance with this project.

Thank you.