The absolute best flying .40 sized sport model ever designed is the Andrews Trainermaster. It was designed by Lou Andrews, the same guy that designed the Aeromaster biplane. The Trainermaster is a low wing fully symetrical design styled to look like a tandem seat military trainer. Kit's are available from Early RC:
The last one I built weighed in at 4 lbs, 8 oz. with HS-225 servos and a 600mA pack. Power was an Irvine .36, though I know of some that were powered by up to .51 sized engines. The closest modern design is a Sportster .40, though they usually weigh half a pound to pound more when finished.
I make the claim of best flying based upon 40 years of flying hundreds and hundreds of different models (thankfully other people supplied 95% of the planes I've flown). Google "trainermaster" and you will find out plenty. It was picked as the Vintage RC design of the year a couple years back, so it has lots of fans.