Sean, that is VERY impressive considering it was taken with 3 tubes and a TC @ f/32!! I tried yesterday with just one tube and my 70-200mm f4 IS on a couple flowers and lost some detail.
Well, here's the latest update on my macro lens saga ...
I sold the lens on the 29th but found out today the $ won't be available until the 8th after first trying paypal & finding out he didn't have the pp funds and then Chase QuickPay and then found out he wasn't even set-up and I'd have to wait for the set-up process. So, this morning I told the guy to forget it. I missed out on a few used macro lenses waiting and I can't shoot with this one in case something were to happen to it. Plus, I've been waiting a week for funds from a guy for my 70-200mm. Stress is high, patience with people is running low!
I'm going to hang on to my 100mm IS for alittle while longer while I practice my Kenko tube skills on the lenses I have left. Since I sold my fav Sigma 85mm last week, I can wait a bit longer on the selling of the macro. Too many lens sales in one week = deep depression anyway!
If my Kenko tube skills don't improve, I decided to either purchase a 100mm non-is or go back to the Sigma 70mm. At least I narrowed it down to the two.
Thank you so much everyone for the suggestions and input! I received a great deal of helpful information even about diffraction, reading charts and lenses in general.