The one thing the person did say is that my coolant flows like a river and that there are no baffles in the top of the radiator to slow down the coolant from flowing so fast. He seemed to think that the coolant is moving too quick and not getting a chance to cool down, thus making the coolant boil over and explode out the overflow bag.
No not true on the rad flowing to fast, anyway it comes out the bottom of the rad, its the thermostat's job to keep the coolant in the block to absorb the heat, the higher the degree thermostat the more heat is taken away, you want the coolant to stay in the motor as long as possible. The pressure cap can be bad and not releasing the pressure it sounds like.
I would try a new pressure cap.