[davidmanze]

I used to shoot macro using a 400 mm lens and tubes. Was great for insects. Great working distance, excellent subject isolation. You may be unfamiliar with this way of shooting close-ups, but that doesn't mean it's no good. In fact it's probably the best way for some subjects.

 I shot a load of butterflies with the Nikor 500mm F4 and a 32mm extension tube, AF worked fine, as you say I was shooting from just  2 meters, otherwise the MFD is 2.8 mts.