What's happening is you are giving too much elevator for the airspeed.

You can make the loops a little smaller, so you won't have lost as much speed by the time you get to the top.

You can try changing to a longer, lower pitch prop; giving more vertical climb authority.

You can reduce the elevator throw... But this one may make it so you can't pull the square corners needed for some maneuvers.

If you can... find a way to reduce tha amunt of dead lead ballast you are using... 3 1/2 oz is a huge amount. Try a heavy hub, or the flywheel style weights that bolt on with the prop (replacing the front prop washer) The further forward the weight it, the less weight you need. .40 size pattern planes need to be kept light.