There are going to be several factors that could contribute to what you are seeing with the CG vs what the manual you found was stating... For instance if you are using a different motor, esc and/or battery than what the manufacturer uses, it could explain a lot.... In this case, if your setup is lighter in weight, that would explain why you need to move back that inch ( or so ) in order to get it to balance.
Until you find someone that has the exact same model... go by the manufacturer recommendations.
Once you do get ( or verify ) the CG... The following can help once you get the initial setup and have gotten it into the air to further tweak the settings... These instructions are made more for 3D and Sport fliers and not trainers that may have a flat bottom wing ( ie Clark Y or modified Clark Y etc )
After reaching a good safe height... a quick way of finding the optimal CG is to pull back to 1/2 throttle at altitude. Fly well above the minimum glide speed - cruising speed. Make several passes up and down the field at several hundred feet, playing with the elevator trim until the airplane flies level with no transmitter inputs.
Leaving the throttle alone, force a 30 to 40 degree dive. When the plane has gained a 20% to 30% increase in speed, (say 50 ft. or so), so that it's accelerating, take your thumb off the stick. If the airplane continues on straight, (hopefully not too long!), it's at the lateral perfect center of gravity. It is neutrally stable. The airplane doesn't change direction, it just keeps on going. If it starts to go up, then it is tail heavy, if it starts going down, it is nose heavy.
If you are a pretty decent pilot... Bring the plane back up to a good safe altitude again and return it to 1/2 throttle... go inverted. If the CG is correct it will either continue straight and level or ( more commonly ) will require a slight down input on the elevator to maintain a level flight path.
Really good pilots will also check the plane in knife edge flight... but I don't recommend it unless you are pretty proficient already.... so I'd suggest you skip this test until you are more experienced.[/QUOTE
When I put the plane on the balancer at the spec. that I found on line, ( 2 1/2 " ) I layed 50 grams on the nose, and it was still way too tail heavy. That is why I figure that it must have been a typo, and the c.g. has to be at one third or less from leading edge. In this case 10.75" wing chord makes the c.g. at about 3 1/2 " and it is pretty good at 3 1/8- 3 3/8 "