I am planning on purchasing either a Great Planes Extra 300 ARF or a World Models Extra 300 ARF (Both are 1/4 scale with 80" wingspans) and should weigh in at around 15-16 lbs. I want to power it with a gas engine. Both manufacturers recommend a 1.60-2.10 2-cycle, a 2.00-3.00 4-cycle, or a 2.5-3.8 cubic inch (41CC-65 CC) gas engine. After being involved in r/c for 15+ years, I have never had a gas airplane. I have looked at BME, Brison, Zenoah, and 3W. I am thinking of going with a 50CC+ sized gas engine. I want this plane to rocket out of a hover, yet have a great idle and reliable, no-fuss performance on top end. I also would like to keep the engine weight as low as possible. What do you recommend?

I have the Brison 3.2 and was very pleased with it until that trainer took out my Edge 540.
20x10 was almost 10,000- rpm. The 22x8 was much better. Due to the electroic ignition, the weight is very light.
I would also look at the ZDZ line and RCS line at http://www.rcshowcase.com/
I have the ZDZ 80 and very impressed with engine and service.
Good Luck,
Twinman
PS Stay away from trainers.....trust me!!

I have a bme 50 in mine and it is a monster in this plane turning a 22-8 zinger pro. see the huge thread at RCU in the arf forum

BME all the way. Power, weigh, using a 22x8 bolley , great combo astro