physics question about pull ups

I was trying to work out the expected height gain from a pull up
Experienced glider pilots say you will get a better pull up with a
heavier glider / water etc.
But I can't see this from my (probably incomplete) equations:

total energy = potential energy + kinetic energy

total energy before pull up = total energy after pull up

m * g * h0 + m * pow(v0, 2) * 0.5 == m * g * h1 + m * pow(v1, 2) * 0.5

with h0 v0 being height and speed before pull up
and h1 v1 being height and speed after pull up

mass cancels out of this equation

I think I need to include momentum in there somehow?