Thanks Al. Must admit that I'm pleased that I can get a bit extra length!! My eyes and heart are still with a 500mm f4 or 600 mmf4 :o:o ( a person must have a dream!!);)
The 500 would be nice but you will be able to do lots of damage with you equipment !!! .... don't get hang up on using the 2X all the time, remember there is a huge penalty in AF performance.