My measurements :

Canon EF 17-40mm/4L USM at infinite
At 17mm : A = 39mm (camera body Canon EOS50D) + 71mm = 110mm (rotation point at 25.5mm from front lens)
At 28mm : A = 39mm (camera body Canon EOS50D) + 69mm = 108mm (rotation point at 27.5mm from front lens)
At 40mm : A = 39mm (camera body Canon EOS50D) + 72mm = 111mm (rotation point at 24.5mm from front lens)

Canon EF 100mm f/2.8 Macro USM at infinite
At 100mm (no choice!) : A = 39mm (camera body Canon EOS50D) + 76mm = 115mm (rotation point at 42.5mm from front lens)

Canon EF 70-200mm f/4 USM at infinite
At 70mm : rotate point at less than 73mm from front lens
At 100mm : A = 39mm (camera body Canon EOS50D) + 80mm = 119mm (rotation point at 92mm from front lens)
At 135mm : A = 39mm (camera body Canon EOS50D) + 43mm = 82mm (rotation point at 129mm from front lens)
At 200mm : A = 39mm (camera body Canon EOS50D) + 40mm = 79mm (rotation point at 132mm from front lens)

For panoramas in the distance, don't be obsessed by precision.

This 100 mega pixels mosaic at 200mm http://www.pbase.com/philway/image/73121804/original
was made with the camera put as if it was the 17-40mm lens.

This panorama at 200mm http://www.pbase.com/philway/image/65266422/original
was made as if it was the 17-40mm lens with a largest/worst optimized distance of 0.6 pixels in PTAssembler.
The rotation point was nevertheless move forward of 61mm.

This panorama http://www.pbase.com/philway/image/64693550/original
was hand held with a plumbline with a largest/worst optimized distance of 2 pixels in PTAssembler.