A few images, each with a full frame downsized image and a 100% crop, of my one and only shooting session with this lens combo. I usually shoot the TC17 on a 300 F/2.8 and 70-200 VR. I don't shoot the 300 F/4 very often since I got the 2.8, but it is a very very fine lens, as you can see here, even "handicapped" by the TC.

As can be seen from the first couple of images, the 300 F/4 has good close focusing quasi-macro capablility that is enhanced with the TC.

All images shot on a monopod. I would not be surprised if the image quality didn't improve a bit if shot from a proper tripod. The squirrel shots in particular, were shot at 1/80s. I was very happy with that but I can't say that is the best the lens can deliver.