Thanks Hossfly and SafeT and all. I have visually checked the datum line with a stretched string (couldn’t get hold of an incident meter) and I believe the stabilizer leading edge level is probably pointing very slightly upward. Anyway, I will try the following lines of action successively.
a. Take out two of the three washers which were placed behind the engine mount to tilt the engine downwards as the engine level was way out of line with everything else.
b. Move the C.G some 2 cm forward.
c. Place a popsicles stick or two under the trailing edge of the wing and observe the changes in fly characteristics of the plane.
d. If all of the above didn’t work I will try to lower the leading edge of the wing; I really don’t know how to do that now but maybe there is way. I will report back once I find a remedy to this plane that wont fly reasonably level when changing speed.