There are no Spitfires involved. Hurricanes are a completely different airplane. As to increased G forces, the location of the weight doesn't matter and the Hurricane Mk IIc with four 20mm cannons is carrying more weight in guns and ammo than the Hurricane Mk IIb will be with twelve .303s.
That said, many pilots removed the outer four .303s from their Hurricane Mk IIb because they said the extra guns had a disproportionately negative effect on handling. Most likely, I would guess, in roll acceleration.