ORIGINAL: RC-FIEND
It's determined because of allot of factors. I will give you some of them.
1 mounted in my trainer this engine never dead sticked , not even once.
Different tank, lines, and engine position. Did you retune the high and low needles when you made this swap? Did you do a nose up test to confirm that the high speed wasn't lean?
2 same plane to different engines , fuel is brand new and a dead stick occurs.
Could be the plane, but it could also be the way you're tuning the engines.
3 cant cut bulk stock away from fuel tank compartment , because of design.
Nope, and you've yet to prove that the design is the cause of your problems.
4 asked the engine forum what was going on and everyone agreed it was the tank height not the position of the engine.
I just read the thread. You're not accurately representing what was said. One person suggested that tuning could be the issue, but you completely ignored that and latched onto tank height. The people were responding with generalities, and I doubt any of them actually have this plane. They were saying tank height COULD be the problem. There are other, and more likely, explanations, such as the engines not being tuned right.
So I am convinced that the design of the plane is incomplete. If you look at the position of the fire wall it is higher than the carburetor when the engine is mounted at 8 O'clock position. The reason I got a flights in is because the plane isn't level when leaving the ground but a balanced plane in flight is level and this is when the stuttering and stalling of the engine begins.
Stuttering and stalling are indicative of an engine that's not tuned right. You had trouble with a Magnum .28, and now you're having trouble with an OS .46 FX (which by the way is WAY TOO MUCH ENGINE FOR THIS PLANE), and you're now condemning the designers?