I know the Nikon flavor of that Sigma lens gets great reviews and I've even seen some great macro shots with it using extension tubes. You should have great results with it. Looking forward to seeing some of your pic's soon. Cudo's (Spelling) to you Dick for steering him in the right direction
and Huntbear if you ever want to go out shooting some place together, I'm down in your area all the time. I live in Glenwood 
Thanks Wazukie!

I would love to see everyone using Professional Lenses like the L series lenses, but I realize that not everyone has the $500 - $1,000 to pay for them. Not only that, but if everyone was using those lenses Prices would skyrocket and there would be massive shortages of the lenses I still want to purchase.

Huntbear asked me a question about using an extender on the Sigma lens. I could not find an answer. Now that I know you have one, I can pass the question off to you!

Can you use a 1.4X or a 2X extender on that lens?
This isn't one of my best photos.

The Eagle was about 200 yards away, so I had to put the 1.4X extender on the 400 mm lens and then I had to Crop the daylights out of the photo to bring the Eagle and his meal in as close as I could.

Hopefully the rest of my photos are better than this one. ( I only took 224 photos today

)
Dick