It really depends upon the center of mass of the boat in relation to the
axle position. If the center of mass is directly above or behind the
axles you will end up with neutral or negative tongue weight(dangerous
situation). Ideally, the center of mass of the boat should be just ahead
of the axles, just enough to give you the tongue weight you're shooting
for. All else being equal/unchanged increasing the tongue length will
increase tongue weight by the amount of extra material in the tongue.
However the longer tongue does have advantages in more predictable
maneuvering/backing, and in longer reach at a shallow angle launch ramp.
Tom.