Thanks for the experiments, it's been interesting to follow how it does with the two TCs (I have the same two but haven't thought of getting them out to use). I haven't been doing much macro in a long time, thought I might since I'm not traveling. I did get the DFA 100 macro out once and enjoyed it.
This lens probably would capable of doing nice macro with the proper attachments.
Another light-hearted, just for fun shot. If this white poodle had been freshly groomed, I think she might have been harder to see.
Taken at White Sands National Park, New Mexico.