Will a 300F4IS (+1.4TCII) work for Vancouver island/hyder?

I was in Northern B.C. last July for about a week. I visited Prince Rupert and the surrounding area, including the Kutzymateen Bear Sanctuary. I used a 50D with the following lenses: Sigma 17-70 OS, Canon 70-200 f4 IS and Canon 300 f4 IS with Kenko 1.4x about half the time.

I found 300mm and 420mm often enough focal length (480mm and 670mm with 1.6 crop factor). The 300 f4 IS is plenty sharp on its own and slight worse but still acceptable with the 1.4x attached. The autofocus and IS on the 300mm not nearly as effective as what you are used to with the 70-200mm particularly when the 1.4x is attached. Handholding a lens 670mm (equivalent) lens from a Zodiac with 1st generation IS was a real challenge! Here are a few examples from the 300mm f4 IS:

300 f4 L IS (without 1.4x)

300 f4 L IS with 1.4x

Jay