I maidened my Rebel Pro with CG 1" behind the former that is behind the wing tube, with 1/5 tank of fuel onboard. It definitely felt tailheavy, but was very flyable and stall still very, very predictable. there are many places online that you will find info about CG location on this and other rebels, but you are right, a simple, or even complicated google search will yield very few results. I guess I just got lucky, in that I stumbled upon that info while browsing Rebel HOT threads, and I had a Rebel HOT before the classic. The HOT came with a manual, and that manual title read "Rebel HOT and Rebel Classic instruction manual".
I'm surprised the classic doesn't come with that same manual. Mine also didn't.
As Dave said, CG in the middle of the tube with an empty tank is still quite nose heavy for this bird.
After maiden on my Pro, I went from dual 2600mah li-ions on the nosegear mount plate, to dual 5200mah li-ions as far up in the nose as I could get them. My CG is now 1/4" behind the tube with 1/4 tank(1.2L) of fuel, and CG feels near perfect.