RE: IN STOCK ALL SIZES OF THE NEW JTEC RADIOWAVE EXTRA 300's
the 300 should balance right on the wing tube. The way we have always balanced them is to assemble the airplane with everything except for the wings and then pick the plane up by the wing tube socket. The plane should sit level or slightly nose forward. Since the 300 has been lightened from the prototype version it may take moving around your batteries to balance it.
That should be a good starting point for the maiden flight. After that you can dial it in how you like it.
Kevin