Now that the Tamron 90mm SP AF f/2.8 Di Macro 1:1 lens is in my possesion, I'm going to make a few observations just in case they are helpful to others considering purchasing this lens for use in studio situations similar to mine.
Lens hood using 1:1 magnification
Some people wondered whether I would be able to use my standard off-camera studio lighting with the lens fully extended and with the lens hood mounted on the lens. I believe using the lens hood will pose no problem. On the other hand, even if it does, the lens will be so close to the subject that the lighting scheme probably would not create the flare or lack of contrast the hood is designed to eliminate. If I somehow come upon a situation when flare or lack of contrast is created when the lens hood is removed, I can always position a flag between the light source and the lens to eliminate that problem.
Lens hood using greater than 1:1 magnification
With the lens fully extended and with one or more extension tubes being used, the chance of being able to properly light the scene while using the lens hood becomes remote. With all three extension tubes used in that situation, it becomes absolutely impossible to light the scene. However, as above, there is no need to use the lens hood in that situation. That's because the lens will be so close to the subject that it would be difficult to come up with a lighting scheme that properly lights the scene and causes flare or lack of contrast.
Use of a polarizer when focus stacking
Now that I have the lens, I realize that my posts earlier in the thread relating to internal focusing foster a misunderstanding I had. This particular lens lacks internal focusing. I incorrectly thought any such lens would rotate when the lens extends and contracts. I now gather from a little bit of reading (you can believe everything you find on the Internet, right?) that some lenses lacking internal focus do indeed rotate and some do not. This particular lens does not rotate, so there will be no need to adjust the polarizer when focus stacking.
Now my only question is why you folks didn't correct me about that?
By the way, Tamron makes a more expensive macro lens at the same focal length that has internal focusing.
The lens manual
The designation,
Di, on the lens means that it is optimized for use with a digital camera. Try your best not to laugh when you see that the manual mentions film three times in a context that are clearly mistakes.