Shell count for SuperNova mag extension

[Rival]

Have SuperNova that can handle 3.5” shells, but I am loading 2.75” shells, so the factory extension said +2, but it will accommodate 3 extra shells.  Would it overwork the spring if I keep loading 7, or just load as many as it fits and don’t worry about it?

[Rival]

Never mind, simple math shows 6x3.5” shells take up more space in the magazine than 7x2.75” shells.