So the first event at my cottage this summer will be a the "Ballast Blast", get off your rocker. Hum that could go bad!
Bring your two sets of 1,2 and 5lbs soft weights and industrial Velcro and we'll figure out where it needs to go. The principals are the same for vbottom, modv and tunnel. The difference is where you put the weight. I have the most experience, with tunnels then MODv.
The variables on a vbottom are fewer so we'll have it figured out in an afternoon before beer.
Yes the "CG" moving forward is a redistribution of the balance point since a tunnel boat has pressure building (lift) in the stern, more prominently that non tunnels(it's a more significant variable). If you drew a force diagram of the boats CG(mass and gravitational centre point) it would be the same, the difference is a new force (lift) which is variable with speed has been added to the stern. In the end yes this needs to be considered when balancing the boat.
I agree the boats balance centre of force moves forward. Since gravity is constant and the boats weight is constant thus the CG does not change, but now I'm being an ass and playing with words, It's winter I'm bored ..
Tunnels don't really transition through a hump, they are a step function, they are packing air or not.