So the weather wasn't so bad to day and I patterned the Iside with the extended choke from my other gun. I used IC (rt. barrel) and LM (left barrel) and found they shot exactly where the original flush chokes shot. The advantage to these are the knurled fronts are substantially thicker than a flush choke and it doesn't hurt to add an inch and a half in length to the barrels. It looks a bit funny but at least they are the black ones so unless you look close it is hard to tell.
I used Coosa's method and in half an hour or less the left barrel printed on the money. What a relief!
Thank you all for all your suggestions and encouragement. I must admit I was surprised that it worked. The first filing moved the pattern right a bit but it was more like extending the pattern and the new area was sparse. The second filing moved the whole pattern maybe 6 inches right which fortunately was exactly what I needed. It was also a round pattern again. I should have taken before and after pics. We were high fiving!
