Needless to say, all weights going into the boat should be mounted as low as possible where you have that option, this particularly applies to batteries and general ballast.
Colin, as a rule of thumb that's ok - but for some hulls
all ballast at the bottom is not the best solution. At worst, it could provide too much righting moment, producing a hull which is toy-like - twitchy and bobby when on the water.
I'm making a large model of HMS Dreadnought, I looked into what metacentric height really means, broke out Flash, and came up with the following tool:
Metacentric height toolYou can drag the sliders to change the CG depth and the degrees of list. If you set the list to a small amount, and slide the CG to a height where's there's a (scale) accurate 4-feet-or-so of MH, the hull looks remarkably unsafe - the CG is well above the waterline.
But it's a big beamy hull, with bilge keels, not much superstructure/windage above the deck, and a load of inertia (at 1/72nd scale). In this state, the hull is
still stable until long after the decks are awash, beyond 45 degrees of list.
The righting moment is lower than the
abatb state, but in reality this'll mean the ship will roll slowly and much more realistically.
Andy
(I should point out that I'm not aiming to recreate the original's MH - my ballast will ensure that the CG is nearer the waterline. I want a safety factor! But this is still well above lining the bottom of the hull with lead sheet or similar.)