The main jet should be properly sized for top end running.... A bigger main is not a "low end" improver.. the main jet has little effect if any on low end.
And larger carbs generally give more top end... and less low end... not more... this is true for virtually all kinds of motors.
But if somebody has tried it on that motor...maybe they can tell what effect it had.
More compression is the biggest helper for low end (other than gearing).
So if you have a head gasket ... you could try running without it as a test.