Dig et al.,
Seems to me like a half loaded question/issue. For sedintary high or even medium volume shooting a heavy gun is needed. No matter the loads, if you are going to shoot 100 plus shells a day the extra weight is necessary. Not to mention, how it helps with gun swing. However, for carrying a gun all day in the era of low bag limits (especially if in hills or difficult terrain) a light gun is wonderful.
Like Chuck and Rev, I was fortunate to be able to spent some time in So. Dakota this year chasing the wily ringneck. Lots of good strong wild birds and the season was almost a month old. One day I carried a 12 Perazzi and 3 days I carried a 20 Sterlingworth with 26" barrels. I would not even take the Perazzi again. The little 5'13oz. Sterlingworth worked like a magic wand. For some reason I shot it well and with one oz. #5s it just flat WHACKED the birds and at pretty significant distances. And, it was a real pleasure to carry.
Now, I ain't takin' the Sterly out to the range to shoot one or two hundered clays even though I can't wait to get it in the field again.
Different tools for different jobs.
The wood pigeon shoot sounds like a great one.
Regards, Jake