I have the CG set at 4.25 on my LT-40 and at fast speeds it climbs as this airframe is designed to do. At half throttle it has level flight.
If you have your nose pitching up excessively, your engines, down thrust angle may be way off. Or you may not have the plan trimmed properly. Or your running to much pitch on the prop. What prop are you running?
Mine has a Magnum.52 four stroke and it took alot of nose weight to balance it.