Sounds like you guys need to learn to hold a double. Always shoot the front trigger first if you want to shoot a double fast and accurate. If you have problems with doubleing then start out with a snap cap in left barrel. An ejector gun will show you if you doubled or not. Non ejector you can put a piece of masking tape on snap cap to show if you doubled. Its very natural to flow from the front trigger to the back when you have shot enough to make it habit. I suggest you get a double shotgun to practice with a lot. No better training than this. Knock on wood I have never doubled a gun and have shot lots of big stuff. My 500 NE weighs 9 lbs 12 oz with no doubles. When I let someone shoot my doubles they only get one live round at a time. I have even seen someone double with a light recoiling gun like a 9.3. Its how you hold it!

Sam