It looks like the 1.7 is working quite well for you!
Thanks, Andy.

I wound up getting 2 to compare. The first pre-owned TC was used in the hawk image above with the purple sky. I'm not sure why there was such a color shift, but every photo taken from that angle has purple sky. Plus it seems to front focus quite a bit.
So I also ordered a refurbished one for comparison (yay, blue sky), but first I need to perform the AF tuning to before determining which one will work best for me. According to reviews, the 1.7x TC hasn't performed as well as the 1.4x. But I am surprised I'm getting these results which are definitely better than I anticipated. :encouragement:
Since I'm not able to hand hold a super zoom (tendonitis in my right hand), I thought I'd have to settle for the focal length that my 300mm f/4 and 1.4x TC provided - and that is 420mm f/5.6. This 1.7x provides a focal length of 500mm f/6.7 (such an unusual aperture) but the aperture is larger than I anticipated. And that is great!