Bogg, check p64, you're off base.
The rhino fire point allows two passengers to shoot out.
However, infantry firing from the vehicle uses different rules than vehicle mounted weapons.
If the vehicle moves at all then the infantry shooting out counts as having moved (so no firing heavy weapons, and RF are limited to close range if you move the transport), and if the vehicle moves more than 12" no weapons may be fired at all.
The strength of the weapon doesn't matter. So you cna move 12" and fire a pair of meltaguns out the top of your rhino