a 120 2stroke definatly over powered for a Hangar-9, the 120 4 stroke is really on the edge of whats needed to fly these lightly built sport warbirds.

if your using a OS engine then a 91 surpass works fine in them for a Saito a 90-100 is plenty of power.

if its a engine you already have you might have to mount the battery in the tail to get it to balance my Hangar-9 planes balanced out perfectly with a OS91 4st.

I would highly recomend doing a search in the warbirds section on the plane there is alot of information and cautions about overpowering the H-9Corsair without strengthening areas like the firewall and wing joints.

I did a search myself and got over 300 results