I have had three engines in my spitfire. They go as follows. OS 120 AX, just like Tevans55 above. Flew the plane well, but you must break in that engine very well to ensure it runs well inverted. Mine ran flawlessly. But as tevans55 noted you also will have to add a lot of weight to the nose. I also added the large battery and made a sheet metal tray that sat above the engine with lots of lead on it. To ensure proper cooling for an engine fully cowled, I opened up the exhaust stacks to ensure proper airlow up the engine and out the stacks.

The next engine I put in the spitfire was an RCGF 26cc. I am converting all my planes to gas because I am tired of having to clean all the oil off the plane. Engine fit in the cowl very well but had terrible power. This engine was extremely underpowered to the point the plane was a handful to fly at full throttle. Many other 26cc engines may fly the plane but the RCGF is a dog. Do not put it in your plane.

After the failure of the 26cc, I upgraded to an MLD 35CC gas engine to ensure that their are no issues of the plane being under powered. I have also come to the conclusion that a proper running engine and good flying plane is always more important than having an engine enclosed. I have the MLD 35cc installed but it is a much longer engine and is causing me to have to move the cowl out an additional 1/2 inch. this is fine with me because it means less weight in the nose but a little work to fill in where the cowl doesn't reach the proper spot on the fuselage. The MLD also drops about 1/2 inch below the cowl.

I know the DLE 30cc will fly this plane extremely well too.

Hope this helps.

Adam