John, I do not think a TC would work well on this lens. It is a wonderful lens on its own, but have never found TC's to be much good on zooms, especially ones that have a 5.6 speed. Maybe be thinking about a prime to reach a bit further. I know this might not be in the budget, but B&H has the Tamron 300 2.8 for $2299 after this mail in rebate. That is the prime that TC's really work well on. Just something to think about.:smile:
Nancy