The OS 120AX definitely is a nitro guzzler. I don't remember my flight times but it was sucking that fuel like it was going out of style. It also made an insane oily mess on the bottom of the plane. Granite the engine was running like a dream but extremely messy. Any of the big 2 stoke glow engines will guzzle nitro fuel and leave a heck of a mess. Thats why I think you will be happiest with the DLE 30. The DLE 20 has great power for its size, but not enough to pull around the spitfire. The spit is going to come in at about 14-15 pounds. Especially after you add a pound of weight to the nose to balance it. So you are going to need the 30 CC's to pull it around and have a little left over just in case.

Hope this helps. I build my planes to fly and fly for a long time. And be easy to make quick adjustments and repairs if needed. No one will notice a big cooling hole in the bottom of the cowling or a muffler sticking out the side of the cowl when it is flying by at over 100mph inverted on the deck. All they will remember is that the plane flies beautifully and that guy never seems to have problems with his planes. So remember a great flying airplane beats a pretty looking paper weight any day. So don't be afraid to cut that cowl and let that engine breathe.

Adam