I don't believe those barrels can be backbored.
They are pretty thin to begin with and they are chrome lined.
Adding a long tang trigger guard will add another ounce or two to the gun as well. The biggest problem with these guns is when a recoil pad is added, it makes them very muzzle light.
You could hollow out the butt some more to partially neutralize that change in balance but since you are using the Limb Saver pad in addition to the decelerator, you will have a very muzzle light gun and there isn't much you can do about it. Not always a bad thing in a grouse gun.
You can backbore chrome bores with a carbide reamer, so the chrome alone would not rule it out. I have never measured the wall thickness and don't know how much is there right now. As stated eralier, backboring would allow me to take an equal amount of weight from the butt, doubling the weight savings. So far i have not been able to justify the cost of the barrel work vs. total weight saved. And likely never will. Plus I think the barrels would not work for steel shot without the chrome lining, and the MN DNR started a 10 year plan to make all state land no-tox. basically i just don't think the gun is worth it. If I am going to spend more on a gun to get it to 5.5# or below i would want it to be an be on a nicer gun, keeping the Bernardelli as-is for rainy days or a loaner gun.
As i stated in my earlier post, I have worked on the gun and after the weight reduction have it perfectly balanced to my liking. Currently it balanced right on the hinge pin with th ebulk of the weight between my hands. I thought about moving the balance point to the rear, since as you say a muzzle-lite grouse gun can be a good thing. (using the slip-pad would make it muzzle-lite, but would only be needed while my spine was healing) When I make the long guard I will keep the weight and balance point right where it is by taking more wood out of the butt. the factory stocks are pretty clunky and I declunkified mine before i bent it, making it much more svelt looking and feeling.
I could not find the Hushpowers on the gambore site
http://www.kentgamebore.com/contact_us.asp . Yes, 30g sounds like a lot for a low recoil 20 ga load! I will call Gambore this week and check on it, as it has definitely piqued my curiosity.
Thanks to eveyrone for the suggestions. I go back to see the neurosurgeon on October 19 and hope to be released to shoot soemthing more than a .22. My dog is pointing and I am seeing a lot of birds. It has been a blast getting pics of him on point as i walk forward to flush the birds, but i am ready shoot with a shotgun instead of a camera