Sorry for the lack of updates, I've been under the weather all week and I've had to reschedule my 'product shoot' for another time. There are two bits of good news though.
First, this Sunday there is a finch and canary show at the local conservatory. Since I have the 70-200 rented for this weekend, I think I just found a good use for the second day of shooting with the lens.
In addition, I have finally sourced a real, actual Macro lens! It's an EF-S 60mm f/2.8 USM. Not quite as nice as the 100mm, but for the price it's a better option at the moment. Hopefully it will be here next week!