This is the 27% Extra-330?

I just recently got one of these. There is a good thread here in th ARF forum on this plane. I'll try to answer some of your questions based on the research I've done and experience I have had...

-A good 50cc engine will work great. I have an RCGF 50 in mine. The power is excellent. Of the ones you mentioned, DA is the cream of the crop. Nothing wrong with the DL though. Plenty of DL's out there and people love them. I'm, not familiar with the Turnigy but I sure do like the price. There are a lot of good gas engines.

-I think GP recommends Futaba 3305 servos. I have Hitec HS-654's in mine. Just make sure you use a good high torque servo with metal gears. The vibration from the gas engine could cause problems with plastic gears. Of course there are super high torque servos out there, ultra fast servos, digital, etc. It just depends if you are a sport flyer, hard-core 3D, competition or whatever.

-You can go with with a lipo and regulator, a lot of people do. I know there are applications for them but I have a pair of 5-cell NimH in my Extra connected in parallel. This gives plenty of capacity and they are doing the job. I have two other larger gas planes done the same way.

-You'll also need an ignition battery since the engines you are looking at have electronic ignition. I'm running a 4-cell 1450mAh NimH in mine. After 3 good flights over the weekend it only took 400mAh to recharge the battery so I could get 5-6 flights easily I think.

You'll also need other miscellaneous items such as heavy duty servo arms, gasoline compatible fuel tubing, a gas conversion stopper for the fuel tank, heavy duty switches, prop, extensions or servo wire, etc.

The plane goes together nice. my only complaint was the opening in the fuselage for the stabilizer. It was a sloppy fit. Make sure you use plenty of epoxy.

The plane flys great. I'm having fun with it so far. Just installed a smoke system the other night. Can't wait to see it in action on Saturday.