Replacing 400mm5.6 with used 500mm 4.5 non-IS good idea?

[pahranagatman]

Thinking of purchasing a used 500mm 4.5 non-IS to replace my 400mm 5.6. It would be used only on a tripod inside of a portable blind. My thinking is that it will do OK without the IS due to the blind keeping the wind off. Any downsides?

I'm starting to do some in flight bird shots too. Switching from joystick to manfrotto gimbal. Will the 500mm be an improvement, or will the extra reach just be a mistake without IS?

The 500mm IS even used is way out of my budget.

[Harv]

You are looking at a lens that has been discontinued a long, long time ago.  I suspect that if you have a problem with the lens, you will NOT find parts for it.